What damages growth is seniority surprisingly, not diversity (5,6)
I believe the answer is:
agent orange
'what damages growth' is the definition.
I don't know anything about this answer so I cannot judge whether this works.
'seniority surprisingly not diversity' is the wordplay.
'seniority' becomes 'age' (I've seen this in other clues).
'surprisingly' indicates an anagram (a surprising ordering of the letters).
'diversity' becomes 'range' (I've seen this in another clue).
'not' with letters rearranged gives 'nto'.
'age'+'nto'+'range'='AGENT ORANGE'
'is' acts as a link.
Can you help me to learn more?
(Other definitions for agent orange that I've seen before include "Controversial weapon" , "A herbicide" , "Dangerous chemical" , "Nasty chemical" , "This takes leaves off" .)