Servant and head gardener upset over tropical tree (8)
I believe the answer is:
mangrove
'tropical tree' is the definition.
'servant and head gardener upset over' is the wordplay.
'servant' becomes 'man' (man is a kind of servant).
'and' says to put letters next to each other.
'head' suggests taking the first letters.
'upset' is an anagram indicator.
The first letter of 'gardener' is 'g'.
'over' with letters rearranged gives 'rove'.
'man'+'g'+'rove'='MANGROVE'
(Other definitions for mangrove that I've seen before include "that grows in swamps" , "Plant growing in swamps" , "Tree growing on tropical coasts and in muddy swamps" , "Strange tree of tropical swamps is a veg, Norma" , "whose roots may be waterlogged" .)