Spread files out on insects (11)
I believe the answer is:
butterflies
'insects' is the definition.
(butterfly is a kind of insect)
'spread files out on' is the wordplay.
'spread' becomes 'butter' (butter is a spread).
'out' indicates anagramming the letters (out can mean wrong or inaccurate).
'on' is an insertion indicator (as in clothing 'on' a person).
'files' is an anagram of 'flies'.
'butter' going inside 'flies' is 'BUTTERFLIES'.
(Other definitions for butterflies that I've seen before include "Nervous sensation" , "Nervous feeling in stomach" , "Painted ladies, for example" , "coppers?" , "Nervous tremors in the stomach" .)