Relaxed midshipman, one captivated by medal (4-5)
I believe the answer is:
easy-going
'relaxed' is the definition.
(similar in meaning)
'midshipman one captivated by medal' is the wordplay.
'midshipman' becomes 'easy' (ref to Frederick Marryat novel Mr Midshipman Easy).
'one' becomes 'i' (roman numeral).
'captivated by' indicates putting letters inside.
'medal' becomes 'gong' (I've seen this before).
'i' put within 'gong' is 'going'.
'easy'+'going'='EASY-GOING'
(Other definitions for easy-going that I've seen before include "Placid and tolerant, relaxed personality" , "Happy-go-lucky" , "Slope" , "Carefree - relaxed" , "Placid and tolerant, not strict" .)