Summarise poem - tie is crooked (9)
I believe the answer is:
epitomise
'summarise' is the definition.
('summarize'->'epitomize' is in my internal thesaurus and 'ize'->'ise')
'poem tie is crooked' is the wordplay.
'crooked' indicates an anagram.
'poem'+'tie'+'is'='poemtieis'
'poemtieis' is an anagram of 'EPITOMISE'.
(Other definitions for epitomise that I've seen before include "Typify (S, not Z)" , "Act as representative" , "Embody perfectly a stated quality" , "in a summary case" , "to be a perfect example" .)