Curry favour with detectives in quad (9)
I believe the answer is:
courtyard
'quad' is the definition.
(I've seen this before)
'curry favour with detectives' is the wordplay.
'curry favour with' becomes 'court' (I can't justify this - if you can you should believe this answer much more).
'detectives' becomes 'Yard' (Scotland Yard, Metropolitan Police HQ).
'court'+'yard'='COURTYARD'
'in' is the link.
Can you help me to learn more?
(Other definitions for courtyard that I've seen before include "Area surrounded by walls or buildings" , "Dry out car in space enclosed by buildings" , "Enclosure open to the sky attached to a house" , "Quadrangle" , "enclosed area" .)