Being delicate makes father be unwell (5)
I believe the answer is:
frail
'being delicate' is the definition.
('frail' can be similar in meaning to 'delicate')
'father be unwell' is the wordplay.
'father' becomes 'fr' (abbreviation as in a priest's title).
'be unwell' becomes 'ail' (synonyms).
'fr'+'ail'='FRAIL'
'makes' is the link.
(Other definitions for frail that I've seen before include "Weak and infirm" , "isn't sturdy" , "Physically feeble" , "Feeble - basket" , "Delicate, fragile" .)