At the sharp end, a legendary fellow obtains sordid gain (4)
I believe the answer is:
pelf
'sordid gain' is the definition.
'pelf' can be an answer for 'gain' (thesaurus). I'm not certain of the 'sordid' bit.
'at the sharp end a legendary fellow' is the wordplay.
'at' says to put letters next to each other.
'end' indicates one should take the final letters.
'a legendary fellow' becomes 'elf' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
The final letter of 'sharp' is 'p'.
'p' put next to 'elf' is 'PELF'.
'obtains' is the link.
Can you help me to learn more?
(Other definitions for pelf that I've seen before include "Contemptuous expression for wealth" , "Lolly" , "ill-gotten gains" , "Money" , "Lucre" .)