Caesar's foot pokes through new special hole in abdomen (8)
I believe the answer is:
spiracle
'hole in abdomen' is the definition.
'caesar's foot pokes through new special' is the wordplay.
'foot' suggests the final letters (in a down clue, the bottom letter).
'pokes through' indicates putting letters inside.
'new' is an anagram indicator.
The final letter of 'caesar' is 'r'.
'special' is an anagram of 'spiacle'.
'r' going into 'spiacle' is 'SPIRACLE'.
(Other definitions for spiracle that I've seen before include "Opening" , "passage through rock" , "Breathing space" , "Whale's blow-hole" .)