See a chap's dressed (4)
I believe the answer is:
clad
'dressed' is the definition.
('clothe' can be a synonym of 'dress')
'see a chap's' is the wordplay.
'see' becomes 'c' (the word for the letter, according to Chambers).
'a chap' becomes 'lad' ('lad' can be a synonym of 'chap'**).
'c'+'lad'='CLAD'
(Other definitions for clad that I've seen before include "Clothed, covered" , "Attired" , "Wearing" , "Invested" , "Decked" .)