Jailbird pre-irons pants (8)
I believe the answer is:
prisoner
'jailbird' is the definition.
(I've seen this in another clue)
'pre-irons pants' is the wordplay.
'pants' indicates anagramming the letters (UK informal term for 'nonsense' or 'rubbish').
'pre'+'irons'='preirons'
'preirons' with letters rearranged gives 'PRISONER'.
(Other definitions for prisoner that I've seen before include "One captured" , "One kept confined" , "The ---, cult 60s TV series" , "Captive, detainee" , "One locked up" .)