You can count on a taxi returning for us (6)
I believe the answer is:
abacus
'you can count' is the definition.
I can't judge whether this defines the answer.
'a taxi returning for us' is the wordplay.
'taxi' becomes 'cab' (synonyms).
'returning' says the letters should be written in reverse.
'for' says to put letters next to each other.
'cab' backwards is '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 "Old counting-frame" , "Very early calculator" , "Old counter" , "As a cub (anag)" , "this adds up" .)