A quid of tobacco combined initially with chop (4)
I believe the answer is:
chew
'a quid of tobacco' is the definition.
(I've seen this in another clue)
'combined initially with chop' is the wordplay.
'initially' suggests taking the first letters.
'with' means one lot of letters go next to another.
'chop' becomes 'hew' (I've seen this before).
The first letter of 'combined' is 'c'.
'c'+'hew'='CHEW'
(Other definitions for chew that I've seen before include "bit of tobacco" , "Ruminate" , "champ" , "Work between teeth, masticate" , "Bite repeatedly" .)