Dad's a dear fellow (3,3)
I believe the answer is:
old man
This clue could be a double definition.
'dad's' is the first definition.
(synonyms)
'a dear fellow' is the second definition.
'old man' can be an answer for 'fellow' (thesaurus). I am not sure about the 'a dear' bit.
Can you help me to learn more?
(Other definitions for old man that I've seen before include "Aged male as informal father" , "Elderly chap" , "Informal name for father, husband or ship's captain" , "Senior citizen" , "Master?" .)