Endless suffering: Boris's heart consumed by power issue (9)
I believe the answer is:
perdition
'endless suffering' is the definition.
'boris's heart consumed by power issue' is the wordplay.
'heart' says to take the centre.
'consumed by' indicates putting letters inside.
'power' becomes 'p'.
'issue' becomes 'edition' (edition is a kind of issue**).
The central letter of 'boris' is 'r'.
'p'+'edition'='pedition'
'r' put into 'pedition' is 'PERDITION'.
(Other definitions for perdition that I've seen before include "Irrevocable spiritual ruin" , "Everlasting punishment" , "Eternal damnation" .)