Waves of poor quality that front of ship circumvents (7)
I believe the answer is:
billows
'waves' is the definition.
(to billow is to wave or swell)
'of poor quality that front of ship circumvents' is the wordplay.
I cannot quite understand how this works, but
'of' could be 'o' and 'o' is present in the answer.
'poor' could be 'ill' (I've seen this before) and 'ill' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
(Other definitions for billows that I've seen before include "Swells" , "Great waves" , "Big waves" .)