Greek character grabbing a marine shows revulsion (6)
I believe the answer is:
nausea
'revulsion' is the definition.
(I've seen this before)
'greek character grabbing a marine' is the wordplay.
'greek character' becomes 'nu' (letter from the Greek alphabet).
'grabbing' means one lot of letters goes inside another.
'marine' becomes 'sea' (both can mean 'of the sea').
'nu' going around 'a' is 'nau'.
'nau'+'sea'='NAUSEA'
'shows' is the link.
(Other definitions for nausea that I've seen before include "Ill-feeling" , "Sick feeling" , "Use an 'a' (anag)" , "Queasy feeling" , "Feeling of revulsion" .)