Cheerful worker follows former hired car (9)
I believe the answer is:
exuberant
'cheerful' is the definition.
(I've seen this in another clue)
'worker follows former hired car' is the wordplay.
'worker' becomes 'ant' (worker is a type of ant).
'follows' means one lot of letters go next to another.
'former' becomes 'ex' (prefix meaning former or onetime).
'hired car' becomes 'uber' (I can't justify this - if you can you should believe this answer much more).
'ex'+'uber'='exuber'
'ant' after 'exuber' is 'EXUBERANT'.
Can you help me to learn more?
(Other definitions for exuberant that I've seen before include "Enthusiastic" , "Vivacious; effusive" , "Exeunt bar, being in high spirits" , "Lively, cheerful" , "Joyously unrestrained" .)