Get king to leave Kiev in discomfort (7)
I believe the answer is:
achieve
'get' is the definition.
(I've seen this before)
'king to leave kiev in discomfort' is the wordplay.
'king' becomes 'K' (abbreviation for king in chess).
'to leave' indicates named letters should be taken away.
'in' indicates putting letters inside.
'discomfort' becomes 'ache' (I've seen this in another clue).
'kiev' with 'k' taken away is 'iev'.
'iev' going inside 'ache' is 'ACHIEVE'.
(Other definitions for achieve that I've seen before include "Attain successfully" , "Have ice (anag.)" , "win" , "Produce" , "Successfully bring off" .)