Travelled around with chap who painted sea creatures (8)
I believe the answer is:
narwhals
'painted sea creatures' is the definition.
The answer and definition can be both animals as well as being plural nouns.
Maybe you can see an association between them that I can't see?
'travelled around with chap who' is the wordplay.
'travelled' becomes 'ran' (running is a kind of traveling).
'around' shows that the letters should be reversed in order.
'with' becomes 'w' (short for with).
'chap who' becomes 'hals' (I can't explain this - if you can you should give a lot more credence to this answer).
'ran' backwards is 'nar'.
'nar'+'w'+'hals'='NARWHALS'
Can you help me to learn more?
(Another definition for narwhals that I've seen is " Tusked whales".)