Ineffective folk to worry about (4)
I believe the answer is:
wets
'ineffective folk' is the definition.
(wet can mean an ineffectual person)
'worry about' is the wordplay.
'worry' becomes 'stew' (I've seen this in another clue).
'about' says the letters should be written backwards.
'stew' reversed gives 'WETS'.
'to' is the link.
(Other definitions for wets that I've seen before include "Applies moisture" , "Moistens" .)