Worried sea dog in rocks (8)
I believe the answer is:
agonised
'worried' is the definition.
(I've seen this before)
'sea dog in rocks' is the wordplay.
'rocks' is an anagram indicator.
'sea'+'dog'+'in'='seadogin'
'seadogin' with letters rearranged gives 'AGONISED'.
(Other definitions for agonised that I've seen before include "Very pained" , "experienced pain" , "Suffered mental anguish" , "San Diego (anagram)" , "Struggled" .)