Could regret me saying it's spacious (5)
I believe the answer is:
roomy
'it's spacious' is the definition.
(synonyms)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for roomy that I've seen before include "generous" , "Commodious" , "Having big space" , "Having plenty of space" , "Comfortably large" .)