There’s one in outer Hackney, darling (5)
I believe the answer is:
honey
'darling' is the definition.
(thesaurus)
'there's one in outer hackney' is the wordplay.
'there's' becomes 'one' (I can't explain this - if you can you should believe this answer much more).
'one in' is an insertion indicator.
'outer' means to remove the middle letters.
'hackney' with its middle taken out is 'hy'.
'one' going within 'hy' is 'HONEY'.
Can you help me to learn more?
(Other definitions for honey that I've seen before include "Sweet term of endearment" , "sweetener" , "Love" , "Hive fluid" , "Sweet stuff - darling" .)