Men put energy into old contest for real money (6,2,5)
I believe the answer is:
pieces of eight
'money' is the definition.
(I've seen this before)
'men put energy into old contest for real' is the wordplay.
I cannot really understand how this works, but
'men' could be 'pieces' ('piece' can be a synonym of 'man') and 'pieces' is found within the answer.
'energy' could be 'e' (physics symbol as in E=mc2) and 'e' is located in the answer.
'old' could be 'o' (common abbreviation eg in OE for Old English) and 'o' is found in the answer.
'contest' could be 'fight' (I've seen this before) and 'fight' is found within the leftover letters.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for pieces of eight that I've seen before include "Old Spanish silver coins" , "In old money" , "Old coins; '---!' (Long John Silver's parrot)" , "Old Spanish coins (sought by pirates)" , "Spanish dollars" .)