Mr Toad an eccentric lacking definite plan (2,6)
I believe the answer is:
at random
'eccentric lacking definite plan' is the definition.
I don't know anything about this answer so I cannot judge whether it can be defined by this definition.
'mr toad an' is the wordplay.
I cannot quite see how this works, but
'mr' could be 'rand' and 'rand' is found within the answer.
'an' could be 'a' and 'a' is located in the answer.
The remaining letters 'tom' is a valid word which might be clued in a way I don't see.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for at random that I've seen before include "Casually" , "willy-nilly" , "Haphazard" , "without purpose" , "without prior arrangement" .)