Forty-one caught by Operation Flower (5)
I believe the answer is:
oxlip
'flower' is the definition.
(I've seen this before)
'forty-one caught by operation' is the wordplay.
'forty' becomes 'XL' (roman numeral).
'one' becomes 'I' (Roman numeral).
'caught by' indicates putting letters inside.
'operation' becomes 'op'.
'xl'+'i'='xli'
'xli' put inside 'op' is 'OXLIP'.
(Other definitions for oxlip that I've seen before include "Flower of the primrose family" , "Type of primula" , "Primrose-cowslip hybrid" , "Flowery name" , "Wildflower" .)