Everyone, say, backed animal movement (10)
I believe the answer is:
allegretto
'movement' is the definition.
(a movement marked to be performed allegretto)
'everyone say backed animal' is the wordplay.
'everyone' becomes 'all' (I've seen this before).
'say' becomes 'eg'.
'backed' says the letters should be written backwards.
'animal' becomes 'otter' (I've seen this before).
'otter' back-to-front is 'retto'.
'all'+'eg'+'retto'='ALLEGRETTO'
(Other definitions for allegretto that I've seen before include "fairly speedily" , "Moving fairly briskly (music)" , "somewhat quick" , "at a fairly brisk rate" , "fairly quickly" .)