Offensive old coach taking on negative football side beginning to object (9)
I believe the answer is:
obnoxious
'offensive' is the definition.
(similar in meaning)
'old coach taking on negative football side beginning to object' is the wordplay.
I cannot quite see how this works, but
'old' could be 'o' (abbreviation) and 'o' is located in the answer.
'negative' could be 'no' (no is a kind of negative) and 'no' is present in the answer.
'side' could be 'xi' (a football team, from Roman numerals for 11) and 'xi' is found within the answer.
'object' could be 'u' (U is an example) and 'u' is found within the answer.
The remaining letters 'bos' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for obnoxious that I've seen before include "Loathsome" , "Foul" , "Thoroughly offensive and objectionable" , "Repugnant" , "Nasty" .)