Is limited, so hiding it is fine (6)
I believe the answer is:
finite
'is limited' is the definition.
('finite' can be similar in meaning to 'limited')
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for finite that I've seen before include "Bounded or limited" , "Circumscribed" , "Having limits, not open-ended" , "Having set limits" , "Limited, not endless" .)