Little followed by lots is unreasonable (1,3,4)
I believe the answer is:
a bit much
'unreasonable' is the definition.
(I've seen this before)
'little followed by lots' is the wordplay.
I cannot really understand how this works, but
'little' could be 'bit' (a small bit) and 'bit' is found in the answer.
'lots' could be 'm' and 'm' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
'is' acts as a link.
Can you help me to learn more?
(Other definitions for a bit much that I've seen before include "over the top" , "unacceptable" , "Somewhat excessive, crossing the permitted line" , "That's not on" , "Contradiction in terms" .)