Dad's right to be normal (3)
I believe the answer is:
par
'be normal' is the definition.
(I've seen this in another clue)
'dad's right' is the wordplay.
'dad' becomes 'pa' (synonyms).
'right' becomes 'r' (common abbreviation).
'pa'+'r'='PAR'
'to' acts as a link.
(Other definitions for par that I've seen before include "Average score for round of golf" , "Standard number of strokes for a golf hole" , "Face value; equal standing" , "Rap to get even" , "Rating of strokes required for hole (golf)" .)