A temptation said to decrease (5)
I believe the answer is:
abate
'decrease' is the definition.
(abating is a kind of decreasing)
'a temptation said' is the wordplay.
'temptation' becomes 'bait' (bait is a kind of temptation).
'said' shows a homophone (sound like).
'bait' sounds like 'bate'.
'a'+'bate'='ABATE'
'to' acts as a link.
(Other definitions for abate that I've seen before include "Become less intense" , "Subside, grow less" , "Become less in intensity" , "Moderate" , "Lessen - cease" .)