Son gets sleep in break (4)
I believe the answer is:
snap
'break' is the definition.
(snapping is a kind of breaking)
'son gets sleep' is the wordplay.
'son' becomes 's'.
'gets' is a charade indicator (letters next to each other).
'sleep' becomes 'nap' (I've seen this before**).
's'+'nap'='SNAP'
'in' is the link.
(Other definitions for snap that I've seen before include "A walk in the park < to shoot" , "Speak irritably; photo" , "Speak irritably; break" , "Click! - a photograph!" , "Unpremeditated - bite" .)