Convincing leading cameraman to shoot The Third Man (6)
I believe the answer is:
cogent
'convincing leading cameraman' is the definition.
'cogent' can be an answer for 'convincing' (thesaurus). I'm not certain of the 'leading cameraman' bit.
'shoot the third man' is the wordplay.
'shoot the third' becomes 'co' (I am not sure about this - if you are sure you should believe this answer much more).
'man' becomes 'gent' (gent is a kind of man).
'co'+'gent'='COGENT'
'to' is the link.
Can you help me to learn more?
(Other definitions for cogent that I've seen before include "Forceful and convincing" , "Strong" , "Compelling or convincing" , "Clearly argued" , "Convincingly argued" .)