Put on to impress (6)
I believe the answer is:
affect
I believe this clue is a double definition.
'put on' is the first definition.
(I've seen this before)
'impress' is the second definition.
(I know that impress can be written as affect)
'to' acts as a link.
(Other definitions for affect that I've seen before include "Pretend - to have influence on events" , "impress" , "It always has a cause" , "Have impact upon" , "Make impression on or arouse sympathy in" .)