Can be hired at six, possibly (5)
I believe the answer is:
taxis
'can be hired' is the definition.
I can't judge whether this defines the answer.
'at six possibly' is the wordplay.
'possibly' is an anagram indicator.
'at'+'six'='atsix'
'atsix' is an anagram of 'TAXIS'.
Can you help me to learn more?
(Other definitions for taxis that I've seen before include "Cabs" , "return to right place" , "Cars with a driver for hire" .)