Lively blackbird without tail seen around religious court (9)
I believe the answer is:
mercurial
'lively' is the definition.
(I've seen this before)
'blackbird without tail seen around religious court' is the wordplay.
'blackbird' becomes 'merle' ('merle' can be a synonym of 'blackbird').
'without tail' means to remove the last letter.
'seen around' is an insertion indicator.
'religious court' becomes 'curia'.
'merle' with its last letter removed is 'merl'.
'merl' enclosing 'curia' is 'MERCURIAL'.
(Other definitions for mercurial that I've seen before include "Changeable in mood" , "Sprightly" , "Temperamental" , "Changing unpredictably" , "lively" .)