Heavenly body giving son a sudden shock (6)
I believe the answer is:
saturn
'heavenly body' is the definition.
(Saturn is an example)
'giving son a sudden shock' is the wordplay.
'giving' means one lot of letters go next to another.
'son' becomes 's' (genealogical abbreviation for son).
'sudden shock' becomes 'turn' (as in a funny turn).
's' next to 'a' is 'sa'.
'sa'+'turn'='SATURN'
(Other definitions for saturn that I've seen before include "Roman god - gas giant" , "The second largest planet" , "Roman god - planet" , "Nearest ringed planet" , "space traveller" .)