Require a bit of fine edging (4)
I believe the answer is:
need
'require' is the definition.
(I know that require can be written as need)
'a bit of fine edging' is the wordplay.
'a bit of' indicates a hidden word.
'NEED' can be found hidden inside 'fine edging'.
(Other definitions for need that I've seen before include "state requiring relief" , "'miss'" , "Want - require(ment)" , "A condition" , "''A friend in .... is a friend indeed''" .)