Little son, worried and frightened (6)
I believe the answer is:
scared
'frightened' is the definition.
('scare' can be a synonym of 'frighten')
'little son worried and' is the wordplay.
'little' means to remove the last letter (the word is not quite complete).
'son' becomes 's'.
'worried' becomes 'cared'.
'and' becomes 'n' (common abbreviation for 'and').
's'+'cared'+'n'='scaredn'
'scaredn' with its final letter removed is 'SCARED'.
(Other definitions for scared that I've seen before include "Afraid, anxious" , "in fright" , "Nervous" , "Afraid of cedars" , "Frightened, alarmed" .)