Call on father to be bold (6)
I believe the answer is:
daring
'bold' is the definition.
(thesaurus)
'call on father' is the wordplay.
'call' becomes 'ring' ('ring' can be a synonym of 'call').
'on' means one lot of letters go next to another.
'father' becomes 'da' (I've seen this in other clues**).
'ring' put after 'da' is 'DARING'.
'to be' is the link.
(Other definitions for daring that I've seen before include "Audacious, bold" , "'Adventurous, bold (6)'" , "Courageous" , "Intrepid" , "Take (control)" .)