Money returned on explosive component (5)
I believe the answer is:
nitre
'explosive component' is the definition.
(I've seen this before)
'money returned on' is the wordplay.
'money' becomes 'tin' (old-fashioned slang term for money).
'returned' says the letters should be written in reverse.
'on' becomes 're' ('on' can be mean 'with reference to').
'tin' reversed gives 'nit'.
'nit'+'re'='NITRE'
(Other definitions for nitre that I've seen before include "what goes into bangers" , "explosive producer?" , "Otherwise saltpetre" , "Sodium nitrate" , "A part of fertilizer" .)