Somebody you start to count on (3)
I believe the answer is:
one
'somebody' is the definition.
(I know this)
'you start to count on' is the wordplay.
I cannot really see how this works, but
'on' is within the answer.
A single letter 'e' 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 one that I've seen before include "Sole; identical" , "Single person or thing" , "doesn't count for much" , "Figure" , "Lowest cardinal number" .)