Contrary commercial jingle (7)

I believe the answer is:

adverse

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'contrary' is the definition.
(synonyms)

'commercial jingle' is the wordplay.
'commercial' becomes 'ad' (abbreviation for advertisement).
'jingle' becomes 'verse' (I can't explain this - if you can you should believe this answer much more).
'ad'+'verse'='ADVERSE'

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(Other definitions for adverse that I've seen before include "Contrary -- inauspicious" , "'Unfavourable, contrary (7)'" , "Opposed to or unfavourable" , "Hostile" , "Inopportune" .)

I've seen this clue in The Globe and Mail.

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