Crook fleeces exec at first, taking half of capital (5)
I believe the answer is:
felon
'crook' is the definition.
(synonyms)
'fleeces exec at first taking half of capital' is the wordplay.
'at first' indicates taking the first letters.
'taking' says to put letters next to each other.
'half of capital' becomes 'lon' (I've seen this in other clues).
The initial letters of 'fleeces exec' is 'fe'.
'fe'+'lon'='FELON'
(Other definitions for felon that I've seen before include "Person who has committed a serious crime" , "Person guilty of grave crime" , "Has conviction" , "Serious criminal" , "A dealer in textile" .)