Chaps upset, caught in a single bloomer (7)
I believe the answer is:
anemone
'bloomer' is the definition.
(anemone is a kind of flowering plant)
'chaps upset caught in a single' is the wordplay.
'chaps' becomes 'men' (I've seen this before).
'upset' is a reversal indicator.
'caught in' indicates putting letters inside.
'single' becomes 'one' (synonyms).
'men' back-to-front is 'nem'.
'a'+'one'='aone'
'nem' placed within 'aone' is 'ANEMONE'.
(Other definitions for anemone that I've seen before include "The flower is no enema" , "Plant of the buttercup family with brightly coloured flowers" , "bloomer" , "Plant; sea creature" , "perennial" .)