Dispatch small end (4)
I believe the answer is:
send
'dispatch' is the definition.
(thesaurus)
'small end' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
's'+'end'='SEND'
(Other definitions for send that I've seen before include "Transmit; post" , "Transmit (message)" , "Consign" , "Forward" , "Mail" .)