Audible sign of hesitation in boy's talk (6)
I believe the answer is:
sermon
'talk' is the definition.
(sermon is a kind of talk)
'audible sign of hesitation in boy's' is the wordplay.
'audible sign of hesitation' becomes 'erm' (I can't justify this - if you can you should give a lot more credence to this answer).
'in' means one lot of letters goes inside another.
'boy' becomes 'son' (synonyms).
'erm' placed inside 'son' is 'SERMON'.
Can you help me to learn more?
(Other definitions for sermon that I've seen before include "Reproving speech (delivered on the Mount?)" , "Preachment" , "Religious exhortation" , "Church address" , "Moralising talk" .)