A boss of a detective department who's hooked? (4,4)
I believe the answer is:
acid head
'a detective department who's hooked?' is the definition.
I can't tell whether this definition defines the answer.
'a boss' is the wordplay.
'boss' becomes 'cidhead' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'a'+'cidhead'='ACID-HEAD'
'of' is the link.
Can you help me to learn more?
(Other definitions for acid head that I've seen before include "One often on a trip" , "possibly keen to take pounds, shillings and pence?" , "one hooked on LSD!" , "LSD user" .)