It's paid us to return to Brideshead (3)
I believe the answer is:
sub
'it's paid' is the definition.
I can't tell whether this defines the answer.
'us to return to brideshead' is the wordplay.
'to return' says the letters should be written backwards.
'to brideshead' becomes 'b' (head letter of 'brides').
'us' back-to-front is 'su'.
'su'+'b'='SUB'
Can you help me to learn more?
(Other definitions for sub that I've seen before include "Junior editor" , "Prefix meaning under or lower" , "Replacement" , "Loan" , "Prefix meaning beneath" .)