Couplet oaf composed is inappropriate (3,2,5)
I believe the answer is:
out of place
Here is my best explanation:
'inappropriate' is the definition.
'couplet oaf composed' is the subsidiary indication.
'composed' is an anagram indicator.
'coupletoaf' anagrammed gives 'outofplace'.
'is' is the link.
(Other definitions for out of place that I've seen before include "inappropriate", "needing to be elsewhere", "Not suited to the occasion" and "incongruous".)