Worried about sea dog in trouble (8)
I believe the answer is:
agonised
'worried' is the definition.
(I've seen this before)
'sea dog in trouble' is the wordplay.
'trouble' indicates anagramming the letters.
'sea'+'dog'+'in'='seadogin'
'seadogin' anagrammed gives 'AGONISED'.
'about' is the link.
(Other definitions for agonised that I've seen before include "suffered torment" , "Struggled" , "Worried greatly" , "Dog in sea (anag) - suffered anguish" , "experienced pain" .)