Source of thickness of Cockney school base? (9)
I believe the answer is:
arrowroot
'source of thickness of cockney school base?' is the definition.
The answer and definition can be both substances as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'cockney school base?' is the wordplay.
'cockney school' becomes ''arrow' ('Harrow' - famous UK public school - said with the 'H' dropped - a cockney accent.).
'base?' becomes 'root' (synonyms).
'arrow'+'root'='ARROWROOT'
Can you help me to learn more?
(Other definitions for arrowroot that I've seen before include "culinary powder" , "Medicinal plant" , "Starchy plant" , "Fine cooking powder" , "that thickens" .)