Reform please, after right's decline... (7)
I believe the answer is:
relapse
'decline' is the definition.
(I've seen this before)
'reform please after right's' is the wordplay.
'reform' is an anagram indicator.
'after' means one lot of letters go next to another.
'right' becomes 'r' (common abbreviation**).
'please' is an anagram of 'elapse'.
'elapse' put after 'r' is 'RELAPSE'.
(Other definitions for relapse that I've seen before include "Sink back into illness" , "Degenerate like pleaser" , "Become ill again" , "Medical setback" , "medical problem" .)