Send Martin’s off on time (8)
I believe the answer is:
transmit
'send' is the definition.
(I know that send is a kind of the transmit)
'martin's off on time' is the wordplay.
'off' indicates an anagram.
'on' says to put letters next to each other.
'time' becomes 't' (abbreviation).
'martins' is an anagram of 'ransmit'.
'ransmit' after 't' is 'TRANSMIT'.
(Other definitions for transmit that I've seen before include "Send from one person to another, or broadcast" , "Pass on (a disease)" , "Send from one place to another" , "put out" , "F. name; Hamlet (anag.)" .)