I get manic about puzzling (9)
I believe the answer is:
enigmatic
'puzzling' is the definition.
(I know that puzzling can be written as enigmatic)
'i get manic about' is the wordplay.
'about' indicates an anagram.
'i'+'get'+'manic'='igetmanic'
'igetmanic' is an anagram of 'ENIGMATIC'.
(Other definitions for enigmatic that I've seen before include "Mysterious or puzzling, like Mona Lisa's smile" , "Cryptic, mysterious" , "Obscure, puzzling" , "with mysterious substance" , "with a mystery ingredient" .)