In preparation for fighting dunderhead, perhaps (6)
I believe the answer is:
toward
'in preparation for' is the definition.
'toward' can be an answer for 'for' (I've seen this in another clue). I'm unsure of the 'in preparation' bit.
'fighting dunderhead perhaps' is the wordplay.
I cannot quite understand how this works, but
'fighting' could be 'war' and 'war' is found within the answer.
'dunderhead' could be 'd' (head letter of 'dunder') and 'd' is present in the answer.
The remaining letters 'to' is a valid word which might be clued in a way I don't understand.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Another definition for toward that I've seen is " In the direction of".)