Cast having hour in drag (5)
I believe the answer is:
throw
'cast' is the definition.
(synonyms)
'hour in drag' is the wordplay.
'hour' becomes 'hr' (synonyms).
'in' means one lot of letters goes inside another.
'drag' becomes 'tow' (towing is a kind of dragging).
'hr' going within 'tow' is 'THROW'.
'having' is the link.
(Other definitions for throw that I've seen before include "Discard" , "Make a pot" , "Form (pot) on a wheel" , "put on floor" , "Light rug" .)