Had tried to, as a son should (6)
I believe the answer is:
sought
'had tried to' is the definition.
I can't judge whether this definition defines the answer.
'a son should' is the wordplay.
'a son' becomes 's' (genealogical abbreviation for son).
'should' becomes 'ought' (synonyms).
's'+'ought'='SOUGHT'
'as' acts as a link.
Can you help me to learn more?
(Other definitions for sought that I've seen before include "Tried to find" , "Searched for - investigated - desired" , "Wanted" , "Attempted to find" , "Looked for" .)