Remain loyal to boy gutted after criticism (5,2)
I believe the answer is:
stick by
'remain loyal to' is the definition.
(I've seen this in another clue)
'boy gutted after criticism' is the wordplay.
'gutted' means to remove the middle letters (to gut something is to remove its insides).
'after' is a charade indicator (letters next to each other).
'criticism' becomes 'stick' (giving someone stick is criticising them).
'boy' with its centre taken out is 'by'.
'by' after 'stick' is 'STICK BY'.
(Another definition for stick by that I've seen is " Support".)