Is concerned about son's pet (6)
I believe the answer is:
caress
'pet' is the definition.
(I know this)
'is concerned about son's' is the wordplay.
'is concerned about' becomes 'cares'.
'cares'+'s'='CARESS'
(Other definitions for caress that I've seen before include "Stoke affectionately" , "pet" , "Stroke lovingly" , "Gentle loving touch" , "Pat" .)