Old taxi worker in high spirits (9)
I believe the answer is:
exuberant
'in high spirits' is the definition.
(I've seen this before)
'old taxi worker' is the wordplay.
'old' becomes 'ex'.
'taxi' becomes 'uber'.
'worker' becomes 'ant' (worker is a type of ant).
'ex'+'uber'+'ant'='EXUBERANT'
(Other definitions for exuberant that I've seen before include "Elated" , "High-spirited" , "Lively, cheerful" , "Abounding in vitality" , "Full of beans" .)