Musical form Gounod normally holds back (5)
I believe the answer is:
rondo
'musical form' is the definition.
(I know that Rondo is a musical form)
'gounod normally holds back' is the wordplay.
'holds' indicates the answer is hidden within the clue.
'back' says the letters should be written in reverse.
'odnor' can be found hidden inside 'gounod normally'.
'odnor' in reverse letter order is 'RONDO'.
(Other definitions for rondo that I've seen before include "Piece written" , "has repetitive theme" , "Type of movement" , "Musical composition with a recurring theme" , "Musical piece with a recurring theme" .)