Lot of protection in South America over cactus (7)
I believe the answer is:
saguaro
'cactus' is the definition.
(I know that saguaro is a type of cactus)
'lot of protection in south america over' is the wordplay.
'lot of' means to remove the last letter (a lot of the word but not all of it).
'protection' becomes 'guard' (I've seen this before).
'in' indicates putting letters inside.
'south america' becomes 'SA' (abbreviation).
'over' becomes 'o' (cricket abbreviation).
'guard' with its last letter taken off is 'guar'.
'sa'+'o'='sao'
'guar' inserted within 'sao' is 'SAGUARO'.
(Other definitions for saguaro that I've seen before include "Giant type of cactus" , "Branched cactus" , "Huge cactus" , "Large branching cactus" .)