A dog died in a Dorset harbour (6)
I believe the answer is:
poodle
'a dog' is the definition.
(poodle is a kind of dog)
'died in a dorset harbour' is the wordplay.
'died' becomes 'd' (abbreviation next to the year of someone's death).
'in' indicates putting letters inside.
'a dorset harbour' becomes 'poole' (I've seen this before).
'd' put within 'poole' is 'POODLE'.
(Other definitions for poodle that I've seen before include "Pet dog with clipped curly coat" , "Curly-haired breed of dog" , "Small dog" , "Pet dog - lackey" , "Pet dog; obsequious chap" .)