Bat turned in flap (3)
I believe the answer is:
tab
'flap' is the definition.
(both can mean a small piece of material)
'bat turned' is the wordplay.
'turned' is a reversal indicator.
'bat' backwards is 'TAB'.
'in' acts as a link.
(Other definitions for tab that I've seen before include "Till bill" , "Flap; meal bill" , "ticket" , "Kind of label for bat" , "The bill in a restaurant" .)