Film the woman's gas (5)
I believe the answer is:
ether
'gas' is the definition.
(thesaurus)
'film the woman's' is the wordplay.
'film' becomes 'ET'.
'the woman' becomes 'her' (pronoun for a woman).
'et'+'her'='ETHER'
(Other definitions for ether that I've seen before include "Once widely-used anaesthetic" , "The gas is there, oddly" , "What's clear" , "Liquid used as anaesthetic/ solvent" , "It could knock you out" .)