Working on film, but it needs translation? Shy about that (10)

'working on film' is the definition.

'but it needs translation? shy about that' is the wordplay.
'needs translation?' indicates an anagram (I've seen 'needing translation' mean this (I've seen this in other clues)).
'shy' becomes 'sling' (I've seen this in other clues).
'about that' means one lot of letters goes inside another.
'but'+'it'='butit'
'butit' is an anagram of 'ubtit'.
'ubtit' put into 'sling' is 'SUBTITLING'.