Prisoner kept in by the authority of succeeding head of government -- this could blow up (9)
I believe the answer is:
gunpowder
'this could blow up' is the definition.
The definition suggests a singular noun which matches the answer.
'prisoner kept in by the authority of succeeding head of government' is the wordplay.
'prisoner' becomes 'pow' (POW is an example).
'kept in' is an insertion indicator.
'by' is a charade indicator (letters next to each other).
'the authority of succeeding head of' becomes 'under' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'government' becomes 'g'.
'under' after 'g' is 'gunder'.
'pow' inserted inside 'gunder' is 'GUNPOWDER'.
Can you help me to learn more?
(Other definitions for gunpowder that I've seen before include "Explosive invented in 9th-century China" , "likely to go up?" , "Ingredient of fireworks" , "Explosive; type of 23 dn" , "Explosive mixture - plot of 1605" .)