Perfectionist rejected best stuff from time to time (7)
I believe the answer is:
fusspot
'perfectionist' is the definition.
(I've seen this before)
'rejected best stuff from time to time' is the wordplay.
'rejected' is a reversal indicator.
'best' becomes 'tops'.
'from time to time' indicates alternate letters (letters removed on a regular basis).
The alternate letters of 'stuff' are 'suf'.
'tops'+'suf'='topssuf'
'topssuf' written backwards gives 'FUSSPOT'.
(Other definitions for fusspot that I've seen before include "I worry" , "Over-fastidious person" , "bit of a worrier" , "Old woman" , "One who gets worked up" .)