Greet son with a stringed instrument (6)
I believe the answer is:
salute
'greet' is the definition.
(saluting is a kind of greeting)
'son with a stringed instrument' is the wordplay.
'son' becomes 's'.
'with' means one lot of letters go next to another.
'stringed instrument' becomes 'lute' (lute is a kind of stringed instrument).
's'+'a'+'lute'='SALUTE'
(Other definitions for salute that I've seen before include "Greet in military fashion" , "Ceremonial firing of guns" , "Pay tribute to; greet" , "Greet in military style" , "Military gesture of respect" .)