Field marshal with army engineers backing victory in battle runs for small lake (5,6)

'field marshal' is the definition.
(German field marshal)

'army engineers backing victory in battle runs for small lake' is the wordplay.
I cannot quite understand how this works, but
'victory' could be 'win' (I've seen this before) and 'win' is located in the answer.
'runs' could be 'rr' (I've seen this in other clues) and 'rr' is found within the remaining letters.
'lake' could be 'l' (geographical abbreviation) and 'l' is present in the answer.
This explanation may well be incorrect...

'with' is the link.