Fall for something old wives claim, talking butterfly (11)
I believe the answer is:
swallowtail
'butterfly' is the definition.
(I've seen this before)
'fall for something old wives claim talking' is the wordplay.
'fall for' becomes 'swallow'.
'something old wives claim' becomes 'tale' (as in an old wives' tale).
'talking' indicates a 'sounds like' (homophone) clue.
'tale' sounds like 'tail'.
'swallow'+'tail'='SWALLOWTAIL'
(Other definitions for swallowtail that I've seen before include "In circle, mythical snake does" , "insect" , "Butterfly" , "coat" .)