No-pressure friendly for supporter (4)
I believe the answer is:
ally
'supporter' is the definition.
(I've seen this before)
'no-pressure friendly' is the wordplay.
'no' is a deletion indicator.
'pressure' becomes 'p' (abbreviation).
'friendly' becomes 'pally' ('pally' can be similar in meaning to 'friendly').
'pally' with 'p' taken out is 'ALLY'.
'for' is the link.
(Other definitions for ally that I've seen before include "Friendly nation" , "He fights on your side" , "Comrade in arms" , "Friend in time of need" , "Someone with whom one is in league" .)