Make a mess of French word for rodent (6)
I believe the answer is:
marmot
'for rodent' is the definition.
(marmot is a kind of rodent)
'make a mess of french word' is the wordplay.
'make a mess of' becomes 'mar' (I can't explain this - if you can you should give a lot more credence to this answer).
'french word' becomes 'mot' (I've seen this in other clues).
'mar'+'mot'='MARMOT'
Can you help me to learn more?
(Other definitions for marmot that I've seen before include "Small burrowing animal of the squirrel family" , "wild rodent" , "Coarse-furred burrowing rodent" , "Stout, burrowing rodent" , "Large burrowing rodent" .)