Only a share, but it could be mistaken for the lot! (4)
I believe the answer is:
some
'only' is the definition.
Both the definition and answer are adjectives. Maybe there's a link between them I don't understand?
'a share but it could be mistaken for the lot' is the wordplay.
I cannot really see how this works, but
'it' could be 'e' ('e' can mean 'electronic' which is similar to 'IT') and 'e' is found within the answer.
'lot' could be 'm' and 'm' is found in the answer.
The remaining letters 'so' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for some that I've seen before include "Part" , "A little; not a little" , "certain" , "Undefined number" , "Unknown or unspecified amount or number" .)