Turned tad grey at sea (7)
I believe the answer is:
gyrated
'turned' is the definition.
(gyrating is a kind of turning)
'tad grey at sea' is the wordplay.
'at sea' indicates an anagram.
'tad'+'grey'='tadgrey'
'tadgrey' anagrammed gives 'GYRATED'.
(Other definitions for gyrated that I've seen before include "What whirling dervishes did" , "Writhed" , "did turns" , "What Turner did" .)