A bit of restraint on a test, say, with a singsong? (8)
I believe the answer is:
intonate
'a singsong?' is the definition.
(I know that singsong is a more specific form of the action intonate)
'a bit of restraint on a test say' is the wordplay.
'a bit of' indicates a hidden word.
'INTONATE' is hidden in the letters of 'restraint on a test say'.
'with' is the link.
(Other definitions for intonate that I've seen before include "chant solemnly" , "say" .)