Poor Annie's crazy (6)
I believe the answer is:
insane
'crazy' is the definition.
(similar in meaning)
'poor annie's' is the wordplay.
'poor' indicates anagramming the letters.
'annies' is an anagram of 'INSANE'.
(Other definitions for insane that I've seen before include "out to lunch" , "Mentally unhinged" , "Anne is (anag) - crazy" , "mad for love?" , "Deranged, crazy" .)