Irregular stones supplied by crude but honest types (5,8)
I believe the answer is:
rough diamonds
'crude but honest types' is the definition.
I don't know anything about this answer so I cannot judge whether this works.
'irregular stones supplied by' is the wordplay.
'irregular' becomes 'rough' (associated in meaning).
'stones' becomes 'diamonds' (I've seen this before).
'supplied by' means one lot of letters go next to another.
'rough'+'diamonds'='ROUGH DIAMONDS'
Can you help me to learn more?
(Other definitions for rough diamonds that I've seen before include "More than one good bloke lacking social graces" , "simple, honest geezers" .)