Arm raised, make out lump (6)
I believe the answer is:
nugget
'lump' is the definition.
(I know that nugget is a type of lump)
'arm raised make out' is the wordplay.
'arm' becomes 'gun' (gun is a kind of arm).
'raised' is a reversal indicator (going up in a down clue).
'make out' becomes 'get' (getting is a kind of making. I am not sure about the 'out' bit.).
'gun' in reverse letter order is 'nug'.
'nug'+'get'='NUGGET'
Can you help me to learn more?
(Other definitions for nugget that I've seen before include "Maxim perhaps" , "valuable bit of information" , "Small lump (of something valuable)" , "small, valuable item" , "Followed on" .)