Exceptionally large or abundant (6)
I believe the answer is:
bumper
This clue is a double definition.
'exceptionally large' is the first definition.
(I've seen this before)
'abundant' is the second definition.
(similar in meaning)
(Other definitions for bumper that I've seen before include "Protective vehicle bar" , "large drink" , "generous amount of alcohol" , "It's a car fender in America" , "Unusually plentiful as a crop may be" .)