Ambassador producing certificate of qualification on time (8)
I believe the answer is:
diplomat
'ambassador' is the definition.
(I've seen this before)
'qualification on time' is the wordplay.
'qualification' becomes 'diploma' (type of academic qualification).
'on' says to put letters next to each other.
'time' becomes 't' (abbreviation).
'diploma'+'t'='DIPLOMAT'
'producing certificate of' acts as a link.
This may not be correct. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for diplomat that I've seen before include "Overseas representative" , "State envoy" , "negotiator" , "envoy, say" , "eg Ambassador" .)