Approaches RN sea exercises (5)
I believe the answer is:
nears
'approaches' is the definition.
('near' can be a synonym of 'approach')
'rn sea exercises' is the wordplay.
'exercises' is an anagram indicator (letters exercise or move around).
'rn'+'sea'='rnsea'
'rnsea' anagrammed gives 'NEARS'.
(Other definitions for nears that I've seen before include "Comes closer" , "is approaching" , "advances" , "Moves closer to" , "Approaches - snare (anag)" .)