Longed to dress Rob in such a suit (10)
I believe the answer is:
pinstriped
'such a suit' is the definition.
(type of suit)
'longed to dress rob' is the wordplay.
'longed' becomes 'pined' ('pine' can be a synonym of 'long').
'to dress' indicates putting letters inside (inserted letters are dressed in another word).
'rob' becomes 'strip' (to strip a place is to rob it).
'pined' enclosing 'strip' is 'PINSTRIPED'.
'in' acts as a link.
(Other definitions for pinstriped that I've seen before include "sort of material" , "such a suit" .)