Short-lived politician suppressed by terrible strain (10)
I believe the answer is:
transitory
'short-lived' is the definition.
('transitory' can be a synonym of 'short-lived')
'politician suppressed by terrible strain' is the wordplay.
'politician' becomes 'tory' (I've seen this before).
'suppressed by' says to put letters next to each other.
'terrible' indicates anagramming the letters.
'strain' with letters rearranged gives 'transi'.
'tory' put after 'transi' is 'TRANSITORY'.
(Other definitions for transitory that I've seen before include "Short-lived" , "Ephemeral" , "Fleeting" , "Here-today-gone-tomorrow" , "Passing" .)