A tall story -- over very quick (5)
I believe the answer is:
alive
'quick' is the definition.
(thesaurus)
'a tall story over very' is the wordplay.
'tall story' becomes 'lie'.
'over' means one lot of letters goes inside another.
'very' becomes 'v' (abbreviation).
'lie' placed around 'v' is 'live'.
'a'+'live'='ALIVE'
(Other definitions for alive that I've seen before include "''Crying cockles and mussels, ..., ..., oh'' (Molly Malone)" , "Still with us" , "answer, as it happens" , "Teeming (with)" , "operative?" .)