Return weapon and obtain small lump of gold (6)
I believe the answer is:
nugget
'small lump of gold' is the definition.
(I've seen this before)
'return weapon and obtain' is the wordplay.
'return' is a reversal indicator.
'weapon' becomes 'gun' (gun is a kind of weapon).
'and' says to put letters next to each other.
'obtain' becomes 'get' (synonyms).
'gun' written backwards gives 'nug'.
'nug'+'get'='NUGGET'
(Other definitions for nugget that I've seen before include "Solid lump of a precious metal" , "bit of treasure" , "small, valuable item" , "valuable bit of information" , "Raw lump (of gold)" .)