Marine animal takes fuel right inside (5)
I believe the answer is:
coral
'marine animal' is the definition.
'coral' can be an answer for 'animal' (coral is a kind of animal). I'm unsure of the 'marine' bit.
'fuel right inside' is the wordplay.
'fuel' becomes 'coal' (coal is a kind of fuel).
'right' becomes 'r' (common abbreviation).
'inside' indicates putting letters inside.
'coal' going around 'r' is 'CORAL'.
'takes' acts as a link.
Can you help me to learn more?
(Other definitions for coral that I've seen before include "Tone" , "Main resident" , "Deep pink colour" , "Shade of pink" , "Shakespeare: 'Full fathom five thy father lies, of his bones are . . . . . made'" .)