The campaign involved with Roy's film-making (14)
I believe the answer is:
cinematography
'film-making' is the definition.
(use of cameras in film-making)
'the campaign involved with roy's' is the wordplay.
'involved with' indicates anagramming the letters (involved can mean confusing or complex).
'the'+'campaign'='thecampaign'
'thecampaign' mixed up with 'roy' gives 'CINEMATOGRAPHY'.
(Other definitions for cinematography that I've seen before include "Art of film-making" , "Art of 26 [MOVING PICTURES]" , "film unit's work" .)