Film of revolutionary fiction from Mid-Devon (4)
I believe the answer is:
veil
'film' is the definition.
(thesaurus)
'revolutionary fiction from mid-devon' is the wordplay.
'revolutionary' shows that the letters should be reversed in order.
'fiction' becomes 'lie' (I've seen this in another clue).
'from' is a charade indicator (letters next to each other).
'mid' means to look at the middle letters.
The centre of 'devon' is 'v'.
'lie'+'v'='liev'
'liev' backwards is 'VEIL'.
'of' acts as a link.
(Other definitions for veil that I've seen before include "Nun's headdress" , "Mask" , "Cover for face etc" , "To obscure" , "coverage" .)