Turn to welcome father, that is, and attempt to offer support (8)
I believe the answer is:
befriend
'support' is the definition.
(I've seen this before)
'turn to welcome father that is' is the wordplay.
'turn' becomes 'bend' (synonyms).
'to welcome' indicates putting letters inside (inserted letters are welcomed in).
'father' becomes 'fr' (abbreviation as in a priest's title).
'that is' becomes 'ie' (abbreviation for id est, 'that is' in Latin).
'fr'+'ie'='frie'
'bend' going around 'frie' is 'BEFRIEND'.
'and attempt to offer' acts as a link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for befriend that I've seen before include "Finer bed (anag.)" , "be matey with" , "Become pally with (someone)" , "Become a pal to" , "Become a companion to" .)