Just me going at half fare (4)

I believe the answer is:

mere

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'just' is the definition.
('just' can mean 'mere' or 'only')

'me going at half fare' is the wordplay.
'going at half' becomes 'r' (I can't justify this - if you can you should give a lot more credence to this answer).
'fare' becomes 'E' (E is an example).
'me'+'r'+'e'='MERE'

Can you help me to learn more?

(Other definitions for mere that I've seen before include "Paltry" , "Simply, nothing more than" , "Previously pure" , "Pure; lake" , "Pool, small lake" .)

I've seen this clue in the Evening Standard.

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