Instrument: I'm clued cryptically, by first of reversals (8)
I believe the answer is:
dulcimer
'instrument' is the definition.
(dulcimer is a kind of instrument)
'i'm clued cryptically by first of reversals' is the wordplay.
'cryptically' indicates anagramming the letters.
'by' is a charade indicator (letters next to each other).
'first of' says to take the initial letters.
The initial letter of 'reversals' is 'r'.
'im'+'clued'='imclued'
'imclued' anagrammed gives 'dulcime'.
'dulcime'+'r'='DULCIMER'
(Other definitions for dulcimer that I've seen before include "Stringed percussion instrument" , "Something instrumental" , "Mild cure for musical instrument" , "Old percussion instrument" , "Old stringed instrument" .)