Old gardener ignored sizes in small block? (4)
I believe the answer is:
adam
'old gardener' is the definition.
'adam' can be an answer for 'gardener' (I've seen this before). I am not sure about the 'old' bit.
'ignored sizes in small block?' is the wordplay.
I cannot really understand how this works, but
'block?' could be 'dam' (damming is a kind of blocking) and 'dam' is located in the answer.
A single letter 'a' remains which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for adam that I've seen before include "Robert ..., ... Clayton" , "Eden inhabitant" , "first in the race?" , "the first orphan?" , "The first known ancestor" .)