Bunk with sheet finally on ready (5)
I believe the answer is:
tripe
'bunk' is the definition.
(thesaurus)
'sheet finally on ready' is the wordplay.
'finally' says to take the final letters.
'on' means one lot of letters go next to another.
'ready' becomes 'ripe' ('ripe' can be similar in meaning to 'ready'**).
The last letter of 'sheet' is 't'.
't'+'ripe'='TRIPE'
'with' acts as a link.
(Other definitions for tripe that I've seen before include "Ruminant's stomach lining" , "Stomach for consumption; nonsense" , "load of rubbish?" , "Pants" , "Edible nonsense?" .)