See a chap getting dressed (4)
I believe the answer is:
clad
'dressed' is the definition.
(to be clad in something is to be dressed in it)
'see a chap getting' 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').
'getting' says to put letters next to each other.
'c'+'lad'='CLAD'
(Other definitions for clad that I've seen before include "Cover with insulation" , "Dressed" , "Wearing" , "Provided with covering" , "in dress perhaps" .)