Agent before noon on road travelling to collect fish (10)
I believe the answer is:
ambassador
'agent' is the definition.
(I've seen this before)
'before noon on road travelling to collect fish' is the wordplay.
'before noon' becomes 'AM' (as in AM on a clock).
'on' means one lot of letters go next to another (in a down clue, letters appear on others).
'travelling' is an anagram indicator.
'to collect' is an insertion indicator (inserted letters are collected by others).
'fish' becomes 'bass' (bass is a kind of fish).
'road' with letters rearranged gives 'ador'.
'ador' enclosing 'bass' is 'bassador'.
'am'+'bassador'='AMBASSADOR'
(Other definitions for ambassador that I've seen before include "voice?" , "High-ranking diplomat" , "diplomatic type" , "Foreign representative" , "In a different case, he could be" .)