Copious, abundant (5)
I believe the answer is:
ample
This clue is a double definition.
'copious' is the first definition.
(synonyms)
'abundant' is the second definition.
(similar in meaning)
(Other definitions for ample that I've seen before include "Sealed glass container for dose of medicine" , "Big" , "Fairly large" , "Plenty, more than enough" , "Plenteous" .)