Came to head of KGB in trouble (4)
I believe the answer is:
woke
'came to' is the definition.
(I've seen this before)
'head of kgb in trouble' is the wordplay.
'head of' says to take the initial letters.
'in' means one lot of letters goes inside another.
'trouble' becomes 'woe' (I've seen this in another clue).
The initial letter of 'kgb' is 'k'.
'k' placed into 'woe' is 'WOKE'.
(Other definitions for woke that I've seen before include "Roused from sleep" , "Ceased to sleep" , "Stopped sleeping" , "Came to" .)