Appear in Cambridge Footlights, say, and behave badly (3,2)
I believe the answer is:
act up
'behave badly' is the definition.
(act up can mean to misbehave)
'appear in cambridge footlights say' is the wordplay.
I cannot really understand how this works, but
'appear' could be 'act' (I've seen this in another clue) and 'act' is located in the answer.
The remaining letters 'up' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
'and' is the link.
Can you help me to learn more?
(Other definitions for act up that I've seen before include "go wrong" , "Behave badly (colloq.)" , "Become unpleasant" , "create fireworks display?" , "Mess about" .)