You can count on a taxi returning with us (6)
I believe the answer is:
abacus
'you can count' is the definition.
I can't tell whether this defines the answer.
'a taxi returning with us' is the wordplay.
'taxi' becomes 'cab' (synonyms).
'returning' shows that the letters should be reversed in order.
'with' is a charade indicator (letters next to each other).
'cab' reversed gives 'bac'.
'a'+'bac'+'us'='ABACUS'
'on' acts as a link.
Can you help me to learn more?
(Other definitions for abacus that I've seen before include "calculator needed" , "summer once?" , "Old calculator" , "It might calculate" , "As a cub (anag)" .)