Queer old dean, say, breaking no promises (10)
I believe the answer is:
spoonerism
'queer old dean' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.
'breaking no promises' is the wordplay.
'breaking' indicates an anagram.
'no'+'promises'='nopromises'
'nopromises' anagrammed gives 'SPOONERISM'.
'say' acts as a link.
Can you help me to learn more?
(Other definitions for spoonerism that I've seen before include "Verbal exchange of leading characters" , "Regular announcement by old clergyman" , "A slip of the tongue? -- no promises (anag)" , "Burly chassis for Shirley Bassey, say?" , "occasional cluing technique" .)