Caught, felon ultimately suffered (6)
I believe the answer is:
nailed
'caught' is the definition.
(I've seen this in another clue)
'felon ultimately suffered' is the wordplay.
'ultimately' indicates one should take the final letters.
'suffered' becomes 'ailed' (ailing is a kind of suffering).
The last letter of 'felon' is 'n'.
'n'+'ailed'='NAILED'
(Other definitions for nailed that I've seen before include "Properly fixed" , "Fixed with a pin" , "snatched" , "Fastened by Daniel" , "Fastened with metal pin" .)