Brood at home, worried about youngster (8)
I believe the answer is:
incubate
'brood' is the definition.
('incubate' can be a synonym of 'brood')
'home worried about youngster' is the wordplay.
'home' becomes 'in' ('he's home' can mean 'he's in').
'worried' becomes 'ate' (something worrying may eat someone up).
'about' says to put letters next to each other.
'youngster' becomes 'cub' (I've seen this in other clues**).
'ate' after 'cub' is 'cubate'.
'in'+'cubate'='INCUBATE'
'at' is the link.
(Other definitions for incubate that I've seen before include "Develop slowly" , "Keep (eggs) warm" , "Hatch eggs by warmth of bird's body" , "nurture" , "Brood" .)