Admonish agent on border circulating genetic material (9)
I believe the answer is:
reprimand
'admonish' is the definition.
(I've seen this before)
'agent on border circulating genetic material' is the wordplay.
'agent' becomes 'rep' (short for representative).
'on' is a charade indicator (letters next to each other) (in a down clue, letters appear on others).
'border' becomes 'rim' (both can mean an edge).
'circulating' shows that the letters should be reversed in order.
'genetic material' becomes 'DNA' (deoxyribonucleic acid).
'dna' written backwards gives 'and'.
'rep'+'rim'+'and'='REPRIMAND'
(Other definitions for reprimand that I've seen before include "Tick off - carpet" , "Formal rebuke" , "Severe telling-off" , "Admonish" , "Formal censure" .)