Pretender in stream, gaining benefit in fighting at the front (6,7)
I believe the answer is:
perkin warbeck
'pretender' is the definition.
(I've seen this before)
'stream gaining benefit in fighting at the front' is the wordplay.
'stream' becomes 'beck' (northern English dialect term for 'stream').
'gaining benefit in' becomes 'perkin' (I can't explain this - if you can you should give a lot more credence to this answer).
'fighting' becomes 'war'.
'at the front' means one lot of letters go next to another.
'perkin'+'war'='perkinwar'
'beck' after 'perkinwar' is 'PERKIN WARBECK'.
'in' acts as a link.
Can you help me to learn more?
(Other definitions for perkin warbeck that I've seen before include "Pretender against Henry VII" , "English pretender" , "Claimant to throne" .)