Circle line does badly, it's revealed (9)
I believe the answer is:
disclosed
'revealed' is the definition.
(disclosing is a kind of revealing)
'circle line does badly' is the wordplay.
'circle' becomes 'disc' (both can mean a round object).
'line' becomes 'l' (used when specifying particular lines from a poem).
'badly' indicates anagramming the letters (letters in the wrong order).
'does' is an anagram of 'osed'.
'disc'+'l'+'osed'='DISCLOSED'
'it's' is the link.
(Other definitions for disclosed that I've seen before include "Revealed" , "Made known" .)