Be bent on taking a condescending attitude (5)
I believe the answer is:
stoop
'be' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.
'bent on taking a condescending attitude' is the wordplay.
'bent' becomes 'set' (synonyms).
'taking' suggests deleting specific letters (take can mean remove or delete).
'a' becomes 'one'.
'condescending attitude' becomes 'oop' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'set'+'on'='seton'
'seton' with 'one' taken away is 'st'.
'st'+'oop'='STOOP'
Can you help me to learn more?
(Other definitions for stoop that I've seen before include "Lower one's standards" , "Bend the body forwards" , "go on a bender?" , "Hunch" , "Sink" .)