Layabouts sitting around trees — quality of uncomfortable ground? (9)

'quality of uncomfortable ground?' is the definition.
(bumpy ground would be uncomfortable to sit on)

'layabouts sitting around trees' is the wordplay.
'layabouts' becomes 'bums' ('bum' can be a synonym of 'layabout').
'sitting around' is an insertion indicator.
'trees' becomes 'pines' (pine is a kind of tree).
'bums' enclosing 'pines' is 'BUMPINESS'.