Design has been put into that man's suit (6)
I believe the answer is:
hearts
'suit' is the definition.
(hearts is a playing card suit)
'design has been put into that man's' is the wordplay.
'design' becomes 'art' (design is an art).
'has been put into' indicates putting letters inside.
'that man's' becomes 'hes' ('he' refers to a man).
'art' placed within 'hes' is 'HEARTS'.
(Other definitions for hearts that I've seen before include "Cores" , "Scots club nickname; suit" , "Scottish footballers" , "Body pumps" , "Playing card suit" .)