Marine mammals confused men at sea (8)
I believe the answer is:
manatees
'marine mammals' is the definition.
'manatees' can be an answer for 'mammals' (manatee is a kind of mammal). I am not sure about the 'marine' bit.
'confused men at sea' is the wordplay.
'confused' is an anagram indicator.
'men'+'at'+'sea'='menatsea'
'menatsea' is an anagram of 'MANATEES'.
Can you help me to learn more?
(Other definitions for manatees that I've seen before include "Men at sea (anag) - aquatic mammals" , "Large plant-eating mammals of tropical waters" , "Sirenians" , "Water creatures" .)