Fool touching gunpowder ingredient (5)
I believe the answer is:
nitre
'gunpowder ingredient' is the definition.
(I've seen this in another clue)
'fool touching' is the wordplay.
'fool' becomes 'nit' (both can mean a stupid person).
'touching' becomes 're' (both can mean concerning or relating to).
'nit'+'re'='NITRE'
(Other definitions for nitre that I've seen before include "Gunpowder ingredient" , "explosive component" , "Also known as salt-petre" , "food preservative" , "safeguard against decay" .)