Skua, say, on rough side bar (7)
I believe the answer is:
seabird
'skua say' is the definition.
(skua is a kind of seabird)
'rough side bar' is the wordplay.
'rough' indicates anagramming the letters.
'side'+'bar'='sidebar'
'sidebar' is an anagram of 'SEABIRD'.
'on' acts as a link.
(Other definitions for seabird that I've seen before include "Gull, for example" , "Gannet possibly" , "gannet, perhaps" , "gull, say" , "Marine creature" .)