Severe piles: sit awkwardly? (8)
I believe the answer is:
pitiless
'severe' is the definition.
(thesaurus)
'piles sit awkwardly?' is the wordplay.
'awkwardly?' indicates anagramming the letters (I've seen 'awkwardly' mean this).
'piles'+'sit'='pilessit'
'pilessit' is an anagram of 'PITILESS'.
(Other definitions for pitiless that I've seen before include "Unrelenting" , "Callous" , "Unfeeling" , "Cold-hearted" , "Remorseless, ruthless" .)