Puritan using speech to probe film (8)
I believe the answer is:
'puritan' is the definition.
(both can mean a sanctimonious person)
'speech to probe film' is the wordplay.
'speech' becomes 'oral' (oral means relating to speech).
'to probe' indicates putting letters inside (probe can mean to poke or prod into).
'film' becomes 'mist' (to film over is to mist or fog over).
'oral' placed inside 'mist' is 'MORALIST'.
'using' acts as a link.
(Other definitions for moralist that I've seen before include "Ail storm (anag)" , "preacher" , "principled person" , "puritan" , "Principled type" .)