My need is improved imagination (5,3)
I believe the answer is:
minds eye
'imagination' is the definition.
(mind's eye is a kind of imagination)
'my need is improved' is the wordplay.
'improved' indicates an anagram.
'my'+'need'+'is'='myneedis'
'myneedis' anagrammed gives 'MINDS EYE'.
(Other definitions for minds eye that I've seen before include "contemplation" , "memory's required" , "The faculty of imagination" .)