Time musical is current (5)
I believe the answer is:
Here is my best explanation:
'is current' is the definition.
'time musical' is the wordplay.
'time' becomes 't'.
'musical' becomes 'rent' (Rent is an example).
(Other definitions for trent that I've seen before include "Chief river of the Midlands", "River at Stoke and Burton", "Crossword frame", "Little Nell family; Eng. river", "River flowing through Nottingham", "Nottingham's river", "Midlands banker", "Major river of England", "Major English river" and "Notts. river".)