Debris scattered around a possible casualty of oil slick
I believe the answer is:
sea bird
'possible casualty of oil slick' is the definition.
I can't tell whether this defines the answer.
'debris scattered around a' is the wordplay.
'scattered' indicates anagramming the letters.
'around' is an insertion indicator.
'debris' is an anagram of 'sebird'.
'sebird' going around 'a' is 'SEA-BIRD'.
Can you help me to learn more?
(Other definitions for sea bird that I've seen before include "Eg, tern or skua" , "one seen flying over ocean" , "Gull, for example" , "Marine avian" , "A gull, for instance" .)