No idea about boy returning with voice so affected (9)
I believe the answer is:
adenoidal
'voice so affected' is the definition.
(a voice might be adenoidal)
'no idea about boy returning' is the wordplay.
'about' is an anagram indicator.
'boy' becomes 'lad' (informal term for boy).
'returning' shows that the letters should be reversed in order.
'lad' in reverse letter order is 'dal'.
'no'+'idea'='noidea'
'noidea' anagrammed gives 'adenoi'.
'adenoi'+'dal'='ADENOIDAL'
'with' acts as a link.
(Other definitions for adenoidal that I've seen before include "with a nasal voice?" , "concerning pharyngeal tonsil" , "affected voice" , "Like glandular tissue at back of nose" , "Having nasal tones" .)