Is he timeless? (3)
I believe the answer is:
tim
'is he' is the definition.
(short for Timothy)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for tim that I've seen before include "Tiny -, Dickens character (A_Christmas Carol)" , "-- Brooke-Taylor, comedian; -- Minchin, comedian" , "Sir -- Rice, lyricist" , "Tiny ..., endearing Dickens boy" , "Little fellow" .)