Airline using carbon in routes supporting token offsets (15)
I believe the answer is:
counterbalances
'offsets' is the definition.
('counterbalance' can be a synonym of 'offset')
'airline using carbon in routes supporting token' is the wordplay.
'airline' becomes 'BA' (British Airways).
'using' says to put letters next to each other.
'carbon in routes' becomes 'lances' (I can't justify this - if you can you should believe this answer much more).
'supporting' is a charade indicator (letters next to each other) (in a down clue, some letters go below others).
'token' becomes 'counter' (counter can mean a token or chip).
'ba'+'lances' is 'balances'.
'balances' put after 'counter' is 'COUNTERBALANCES'.
Can you help me to learn more?