Policeman and soldiers discover source of oil (5)
I believe the answer is:
copra
'source of oil' is the definition.
(I've seen this before)
'policeman and soldiers' is the wordplay.
'policeman' becomes 'cop' (slang term).
'and' is a charade indicator (letters next to each other).
'soldiers' becomes 'RA' (abbreviation for Royal Artillery).
'cop'+'ra'='COPRA'
'discover' acts as a link.
I am not very happy about this link. It may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for copra that I've seen before include "Nutty product" , "Oil producer" , "Dried cocoa-nut kernels, source of oil" , "Coconut's kernel" , "Dried coconut-kernel" .)