After draining cuppa, Herb put on air-conditioning in US car (8)
I believe the answer is:
cadillac
'us car' is the definition.
(I've seen this before)
'after draining cuppa herb put on air-conditioning' is the wordplay.
'after' is a charade indicator (letters next to each other).
'draining' suggests removing the centre (I've seen 'drained' mean this).
'herb' becomes 'dill' (dill is a kind of herb).
'put on' is a charade indicator (letters next to each other) (some letters go on or after others).
'air conditioning' becomes 'AC'.
'cuppa' with its middle removed is 'ca'.
'ca' next to 'dill' is 'cadill'.
'cadill'+'ac'='CADILLAC'
'in' is the link.
(Other definitions for cadillac that I've seen before include "Luxury US car" , "Car maker" , "Make acid call to car company" , "American brand of luxury car" , "Make an acid call for the US car" .)