Waylaid mum returned exhausted (8)
I believe the answer is:
ambushed
'waylaid' is the definition.
('ambush' can be a synonym of 'waylay')
'mum returned exhausted' is the wordplay.
'mum' becomes 'ma' (ma can mean mother).
'returned' says the letters should be written in reverse.
'exhausted' becomes 'bushed' (bushed can informally mean exhausted).
'ma' written backwards gives 'am'.
'am'+'bushed'='AMBUSHED'
(Other definitions for ambushed that I've seen before include "taken, surprisingly" , "Lay in wait and waylaid" , "Attacked (someone) from concealment" , "surprised?)" , "Taken by surprise in war" .)