Idlers regularly mend ship (8)
I believe the answer is:
despatch
'ship' is the definition.
(despatching is a kind of shipping)
'idlers regularly mend' is the wordplay.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
'mend' becomes 'patch' (patching is a kind of mending).
The alternate letters of 'idlers' are 'des'.
'des'+'patch'='DESPATCH'
(Other definitions for despatch that I've seen before include "Send off, kill" , "Send away" , "Send out - chest pad (anag)" , "Bulletin" , "expedition" .)