Relaxing set grin is problematic (7)
I believe the answer is:
resting
'relaxing' is the definition.
(I've seen this in another clue)
'set grin is problematic' is the wordplay.
'is problematic' indicates anagramming the letters.
'set'+'grin'='setgrin'
'setgrin' is an anagram of 'RESTING'.
(Other definitions for resting that I've seen before include "Taking a break" , "Lying down" , "(Of actors) currently unemployed" , "(Of actor) not working" , "not in a cast" .)