Lively girl accepting offer dispensing with old perfume (12)
I believe the answer is:
effervescent
'lively girl accepting offer dispensing with old perfume' is the definition.
I can't judge whether this defines the answer.
'lively girl accepting offer dispensing with old perfume' is the wordplay.
'lively girl' becomes 'eve' (I am not sure about the 'lively' bit.**).
'accepting' is an insertion indicator.
'dispensing with' indicates named letters should be taken away.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'perfume' becomes 'scent' ('scent' can be a synonym of 'perfume').
'offer' with 'o' taken away is 'ffer'.
'eve' enclosing 'ffer' is 'efferve'.
'efferve'+'scent'='EFFERVESCENT'
(Other definitions for effervescent that I've seen before include "Bubbly" , "Sparkling" , "Fizzy" .)