Maybe it's in part of the Bronx you'll find a source of refreshment (6)

'refreshment' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.

'maybe it's in part of the bronx you'll find a source of' is the wordplay.
'maybe' indicates an anagram.
'in' means one lot of letters goes inside another.
'part of' indicates taking the first letters (I've seen 'part' mean this).
'you'll find' becomes 'r' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'a source' suggests taking the first letters (I've seen 'sources of' mean this (the beginning of a word is its sauce)).
The initial letter of 'bronx' is 'b'.
The initial letter of 'of' is 'o'.
'its' anagrammed gives 'ist'.
'b'+'r'='br'
'ist' inserted within 'br' is 'bistr'.
'bistr'+'o'='BISTRO'

Can you help me to learn more?