Drug squad member working on a lead? (6,3)
I believe the answer is:
police dog
'drug squad member' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'working on a lead?' is the wordplay.
I cannot really understand how this works, but
'lead?' could be 'do' (leading is a kind of doing) and 'do' is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for police dog that I've seen before include "one taking lead in war on crime" , "Force assistant" , "Officer's co-worker" , "Canine for the boys in blue" , "Drug hunter" .)