Moon produces little change in rough sea (9)
I believe the answer is:
satellite
'moon' is the definition.
(thesaurus)
'little change in rough sea' is the wordplay.
'change' indicates an anagram.
'in' is an insertion indicator.
'rough' indicates anagramming the letters.
'little' is an anagram of 'tellit'.
'sea' anagrammed gives 'sae'.
'tellit' placed into 'sae' is 'SATELLITE'.
'produces' acts as a link.
(Other definitions for satellite that I've seen before include "Orbiter of planet" , "Body that revolves around or serves another" , "sidekick" , "outpost" , "Country dependent on another" .)