Unhappy about site, if remarkably content (9)
I believe the answer is:
satisfied
'content' is the definition.
(similar in meaning)
'unhappy about site if remarkably' is the wordplay.
'unhappy' becomes 'sad' (associated in meaning).
'about' is an insertion indicator.
'remarkably' indicates anagramming the letters.
'site'+'if'='siteif'
'siteif' anagrammed gives 'tisfie'.
'sad' going around 'tisfie' is 'SATISFIED'.
(Other definitions for satisfied that I've seen before include "served" , "Complied with (a condition)" , "given answer > was convincing" , "Content" , "relieved of doubt" .)