Dad got one right in two (4)
I believe the answer is:
pair
'two' is the definition.
(pair is a kind of two)
'dad got one right' is the wordplay.
I cannot really understand how this works, but
'dad' could be 'pa' (both can mean one's father) and 'pa' is present in the answer.
'one' could be 'i' (Roman numeral) and 'i' is located in the answer.
'right' could be 'r' (abbreviation) and 'r' is found in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
'in' acts as a link.
Can you help me to learn more?
(Other definitions for pair that I've seen before include "Twosome" , "Duo" , "E.g. two aces; mate" , "Cereal used as food" , "Set of two" .)