Ravana came to seeta's place in disguise of an ascetic.
I want to know exact description of what actually he looked like?
From head to toe.
The description is given in Valmiki Ramayan: Aranya Kanda: Sarga 46:
तदा आसाद्य दशग्रीवः क्षिप्रम् अंतरम् आस्थितः |
अभिचक्राम वैदेहीम् परिव्राजक रूप धृक् || ३-४६-२
श्लक्ष्ण काषाय संवीतः शिखी चत्री उपानही |
वामे च अंसे अवसज्य अथ शुभे यष्टि कमण्डलू || ३-४६-३
परिव्राजक रूपेण वैदेहीम् अन्ववर्तत |
Quickly taking hold of intervallic time then the ten-headed Ravana approached Vaidehi adopting an aspect of a sanyaasi, a meandering Brahman friar. [3-46-2]
That sanyaasi is now cloaked in smooth silky saffron, his head-hair is neatly tufted, sandals are wooden, umbrella is on right shoulder, and on his left shoulder a shaft of sanyaasi is shouldered, onto which his handy water vessel is hooked, and he proceeded towards Vaidehi in a mien of meandering sanyaasi. [3-46-3, 4a]
The tenheaded Ravana who was in hiding assumed the guise of a wandering mendicant and approached Sita.
And then Ravana wearing fine orange robes, with hair knotted on the head, carrying a parasol, wearing sandals, hanging a kamandalu (waterpot), and a staff on the auspicious left shoulder walked towards Vaidehi like a mendicant.
The below commentary on the above shlokas is also relevant:
There are many dress rules to a sanyasi 'the Hindu sanyaasi' where the main items are, as said by Sage Angiirasa: brahma suutram tridanDam ca vastram jantu nivaaraNam | shikyam paatram bR^isiim caiva kaupiinam kaTi veShTitam 'sacred thread, three-shafts, saffron clothing, deerskin, handy water vessel, grass-mat, loin-cloth, girdle-cloth... by these he will be known as a real sanyasi 'Hindu sanyaasi.' Out of all these items, the shafts make a difference. Vaishnavaite sanyaasi-s handle three shafts tied into one, and the three are symbolic to cit, acit, iishvara 'animate, inanimate, and lord...' and on this Manu says vaak daNDaH ca mano daNDaH kaaya daNDaH tathaiva ca | yasya ete nihitaa buddhau sa tridaNDii ca ucya te the word daNDa means 'repressing, suppression, control...' thus a sanyaasi has to control his 'speech, mind, and body... by that alone he is renowned as sanyasi... Manu. As such, Ravana is in the getup of an unmistakable Brahman sanyaasi, with an unbridled tongue.