Loud speaker's overly sentimental period cut short at school (8)
I believe the answer is:
tweeters
'loud speaker's' is the definition.
'tweeter's' can be an answer for 'speaker's' (tweeter is a type of loud speaker). I am not sure about the 'loud' bit.
'overly sentimental period cut short at school' is the wordplay.
'overly sentimental' becomes 'twee' (I've seen this before).
'period' becomes 'term' (term is a kind of period).
'cut short' means to remove the last letter.
'at' is a charade indicator (letters next to each other).
'school' becomes 'S'.
'term' with its last letter removed is 'ter'.
'twee'+'ter'+'s'='TWEETERS'
Can you help me to learn more?
(Other definitions for tweeters that I've seen before include "Speakers" , "Users of Twitter social network" , "Speaker systems and Twitter users" .)