Coat perhaps keeps flashing inside leg area (9)
I believe the answer is:
sheepskin
'coat perhaps' is the definition.
'keeps flashing inside leg area' is the wordplay.
'flashing' indicates anagramming the letters (flash can mean to move around).
'inside' is an insertion indicator.
'leg area' becomes 'shin'.
'keeps' with letters rearranged gives 'eepsk'.
'eepsk' inserted into 'shin' is 'SHEEPSKIN'.
(Other definitions for sheepskin that I've seen before include "Woolly pelt" , "Ovine outer layer used in coats and rugs" , "Body covering of an ovine mammal" , "coat" , "Fleece garment" .)