Certain policemen, indeed, are emphatic! (7)
I believe the answer is:
decided
'emphatic' is the definition.
(thesaurus)
'certain policemen indeed' is the wordplay.
I cannot quite see how this works, but
'policemen' could be 'cid' (abbreviation for Criminal Investigation Department) and 'cid' is located in the answer.
The remaining letters 'deed' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
'are' is the link.
Can you help me to learn more?
(Other definitions for decided that I've seen before include "Definite; agreed" , "Made mind up, being unequivocal" , "Resolved, settled" , "Indisputable" , "Unquestionable" .)