Lad very embarrassed to admit papa's promised money (9)
I believe the answer is:
sponsored
'promised money' is the definition.
Although both the answer and definition are past participle verbs, I can't understand how one could define the other.
'lad very embarrassed to admit papa's' is the wordplay.
'lad' becomes 'son' (lad can informally mean a young boy).
'very' becomes 'so' (both can mean 'extremely').
'embarrassed' becomes 'red' (someone may blush or go red when embarrassed).
'to admit' indicates putting letters inside.
'papa' becomes 'P' (phonetic alphabet: alpha, bravo, charlie etc.).
'son'+'so'+'red'='sonsored'
'sonsored' placed around 'p' is 'SPONSORED'.
Can you help me to learn more?
(Other definitions for sponsored that I've seen before include "With backing" , "(Of event) supported financially" .)