One's fretted over time, Cautious Craig in bits (8,6)
I believe the answer is:
acoustic guitar
'one's fretted' is the definition.
I can't judge whether this defines the answer.
'time cautious craig in bits' is the wordplay.
'time' becomes 't' (abbreviation).
'in bits' indicates an anagram (the bits of the anagram are rearranged).
't'+'cautious'+'craig'='tcautiouscraig'
'tcautiouscraig' anagrammed gives 'ACOUSTIC GUITAR'.
'over' acts as a link.
Can you help me to learn more?
(Another definition for acoustic guitar that I've seen is " Unamplified instrument".)