Absolutely right boy collecting trophy (4-2)
I believe the answer is:
spot-on
'absolutely right' is the definition.
(I've seen this before)
'boy collecting trophy' is the wordplay.
'boy' becomes 'son' (synonyms).
'collecting' means one lot of letters goes inside another.
'trophy' becomes 'pot' (type of trophy).
'son' enclosing 'pot' is 'SPOT-ON'.
(Other definitions for spot-on that I've seen before include "Completely accurate" , "'Exactly right (4,2)'" , "Informally - exactly so, precisely" , "On the nail" , "Informally precise, receiving no post" .)