Might use a jemmy? (5)
I believe the answer is:
force
'might' is the definition.
(I've seen this in another clue)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for force that I've seen before include "cascade of water" , "Vehemence" , "Physical coercion" , "Power; army" , "'Compel, pressurise (5)'" .)