Bob, say, helmeted Irish copper? (7)
I believe the answer is:
haircut
'bob say helmeted' is the definition.
(I know that bob is an haircut)
'irish copper?' is the wordplay.
I cannot really understand how this works, but
'irish' could be 'ir' (abbreviation) and 'ir' is found within the answer.
'copper?' could be 'cu' (chemical symbol) and 'cu' is found in the answer.
The remaining letters 'hat' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
(Other definitions for haircut that I've seen before include "Tonsorial style" , "Trim on top" , "Mohican, possibly" , "Bob, say" , "Bob maybe" .)