A father must entertain quiet hope (6)
I believe the answer is:
aspire
'hope' is the definition.
(thesaurus)
'a father must entertain quiet' is the wordplay.
'father' becomes 'sire' ('sire' can be a synonym of 'father').
'must entertain' is an insertion indicator.
'quiet' becomes 'p' (music symbol for 'piano').
'sire' placed around 'p' is 'spire'.
'a'+'spire'='ASPIRE'
(Other definitions for aspire that I've seen before include "Hope (to do something)" , "Have a strong desire to reach an objective" , "Hope, dream" , "Have ambition or desire for praise" , "Have an ambitious plan or a lofty goal" .)