Hope earnestly not to be short (4)
I believe the answer is:
long
'not to be short' is the definition.
('long' is the opposite to 'short')
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for long that I've seen before include "summer break?" , "hunger" , "extended period" , "Protracted" , "Sustained" .)