Catch son leaving home (3)
I believe the answer is:
net
'catch' is the definition.
(net can mean to catch)
'son leaving home' is the wordplay.
'son' becomes 's' (genealogical abbreviation for son).
'leaving' is a deletion indicator.
'home' becomes 'nest' (a bird's home).
'nest' with 's' taken away is 'NET'.
(Other definitions for net that I've seen before include "Mesh; profit" , "Lattice" , "Fine open-weave fabric" , "Capture" , "device to divide the court" .)