Hardly hard currency! (5)

I believe the answer is:

dough

I'm a little stuck... Click here to teach me more about this clue!

'currency' is the definition.
(thesaurus)

'hardly hard' is the wordplay.
'hardly' becomes 'doug' (I can't justify this - if you can you should believe this answer much more).
'hard' becomes 'h' (abbreviation used in pencil classifications).
'doug'+'h'='DOUGH'

Can you help me to learn more?

(Other definitions for dough that I've seen before include "cash" , "Bread-paste" , "'Dosh'" , "Moistened flour" , "Bread mixture; money" .)

I've seen this clue in the Evening Standard.

Want a hint initially instead of a full solution? Install my app