The rule for keeping a guerrilla leader in check (5)
I believe the answer is:
reign
'the rule' is the definition.
(reign is a kind of rule)
'keeping a guerrilla leader in check' is the wordplay.
'keeping' means one lot of letters goes inside another (some letters kept inside).
'leader' indicates taking the first letters.
'in check' becomes 'rein' (both can mean to control or limit. I am not sure about the 'in' bit.).
The initial letter of 'guerrilla' is 'g'.
'g' placed within 'rein' is 'REIGN'.
'for' acts as a link.
Can you help me to learn more?
(Other definitions for reign that I've seen before include "Rule - dominate" , "Monarch's rule" , "Time on throne" , "Rule of monarch" , "Hold sway, rule" .)