Picture one game in operation (7)
I believe the answer is:
imagine
'picture' is the definition.
(picture can mean to visualise or imagine)
'one game in operation' is the wordplay.
I cannot really see how this works, but
'one' could be 'i' (Roman numeral) and 'i' is present in the answer.
'game' could be 'gin' (gin is a kind of game) and 'gin' is found within the answer.
The remaining letters 'mae' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for imagine that I've seen before include "Lennon song - dream" , "Picture to oneself" , "Number one" , "Enigma, I? (anag)" , "Suspect" .)