She finally received rent as morale-booster (3,4)
I believe the answer is:
ego trip
'morale-booster' is the definition.
(something to boost one's ego or morale)
'she finally received rent' is the wordplay.
'finally' suggests the final letters.
'received' becomes 'got' ('get' can be a synonym of 'receive').
'rent' becomes 'rip' (rent can mean a tear in something).
The last letter of 'she' is 'e'.
'e'+'got'+'rip'='EGO-TRIP'
'as' is the link.
(Other definitions for ego trip that I've seen before include "self-centred indulgence" , "Action that inflates one's self-importance" , "a vain experience" , "Something increasing one's self-importance" , "Self-glorification episode" .)