First person wearing simple medal is placid (4-5)
I believe the answer is:
easy-going
'placid' is the definition.
(I've seen this before)
'first person wearing simple medal' is the wordplay.
'first person' becomes 'I' (first-person pronoun).
'wearing' indicates putting letters inside.
'simple' becomes 'easy' (similar in meaning).
'medal' becomes 'gong' (informal term for a medal or prize).
'easy'+'gong'='easygong'
'i' put into 'easygong' is 'EASY-GOING'.
'is' is the link.
(Other definitions for easy-going that I've seen before include "Calm - relaxed - nonchalant" , "Hairdresser's shop" , "Placid and tolerant, relaxed personality" , "Laid back" , "Slope" .)