Steal diamonds, maybe, and set of clothes (7,4)
I believe the answer is:
trouser suit
'steal diamonds' is the definition.
The definition suggests a singular noun which matches the answer.
'maybe and set of clothes' is the wordplay.
'maybe' becomes 'trouser' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'and' says to put letters next to each other.
'set of clothes' becomes 'suit' (I've seen this before).
'trouser'+'suit'='TROUSER SUIT'
Can you help me to learn more?
(Other definitions for trouser suit that I've seen before include "Two-piece costume" , "female outfit" , "A matching jacket and pants" , "two-piece attire" , "Two-piece wear for woman" .)