Unfavourable publicity given to metrical composition (7)
I believe the answer is:
'unfavourable' is the definition.
(similar in meaning)
'publicity given to metrical composition' is the wordplay.
'publicity' becomes 'ad' (short for advert).
'given to' is a charade indicator (letters next to each other).
'metrical composition' becomes 'verse' (I can't justify this - if you can you should give a lot more credence to this answer).
Can you help me to learn more?
(Other definitions for adverse that I've seen before include "Opposed to or unfavourable" , "Dire" , "Hostile" , "Detrimental" , "Contrary -- inauspicious" .)