Orchestra’s trio, perhaps, struck second sleigh bells, say? (9)
I believe the answer is:
syllables
'orchestra's trio perhaps' is the definition.
I can't judge whether this defines the answer.
'struck second sleigh bells say?' is the wordplay.
'struck' is an anagram indicator (I've seen this in other clues).
'second sleigh' becomes 'l' (2nd letter of 'sleigh').
'l'+'bells'+'say'='lbellssay'
'lbellssay' with letters rearranged gives 'SYLLABLES'.
Can you help me to learn more?
(Other definitions for syllables that I've seen before include "Individual sounds in a word" , "Unit of spoken language" , "Units of spoken language" , "Units in a word" .)