A son straying in shot, showing surprise (8)
I believe the answer is:
astonish
'surprise' is the definition.
(I've seen this before)
'a son straying in shot' is the wordplay.
'son' becomes 's'.
'straying' indicates an anagram.
'in'+'shot'='inshot'
'inshot' anagrammed gives 'tonish'.
'a'+'s'+'tonish'='ASTONISH'
'showing' acts as a link.
(Other definitions for astonish that I've seen before include "Floor" , "Amaze, astound" , "are staggering" , "Startle" , "Take by surprise" .)