Nice guys soften up entering grand spaces (9)
I believe the answer is:
gentlemen
'soften up entering grand spaces' is the definition.
I can't tell whether this defines the answer.
'nice guys' is the wordplay.
'nice' becomes 'gentle' (I can't explain this - if you can you should give a lot more credence to this answer).
'guys' becomes 'men' (guy can mean a man).
'gentle'+'men'='GENTLEMEN'
Can you help me to learn more?
(Other definitions for gentlemen that I've seen before include "fellows held to be considerate?" , "Males of good standing" , "'Time ____ 15!'" , "Males of refinement" , "with a preference for the flaxen-haired?" .)