The comrades get sea sick in turn (6)
I believe the answer is:
allies
'the comrades' is the definition.
(I've seen this in another clue)
'sea sick in turn' is the wordplay.
'sick' becomes 'ill' (similar in meaning).
'in' means one lot of letters goes inside another.
'turn' says the letters should be written backwards.
'sea' enclosing 'ill' is 'seilla'.
'seilla' in reverse letter order is 'ALLIES'.
'get' is the link.
(Other definitions for allies that I've seen before include "They join and fight together" , "Nations working together" , "Colleagues" , "Joins forces" , "They are banded together for mutual support" .)