Papa with family forms to fill out (7)
I believe the answer is:
amplify
'fill out' is the definition.
(thesaurus)
'papa with family forms' is the wordplay.
'papa' becomes 'p' (phonetic alphabet: alpha, bravo, charlie etc.).
'with' says to put letters next to each other.
'forms' indicates an anagram.
'p' after 'family' is 'familyp'.
'familyp' is an anagram of 'AMPLIFY'.
'to' acts as a link.
(Other definitions for amplify that I've seen before include "Make fuller, increase the strength of" , "Add strength or details to" , "Expand" , "Increase the strength of, say sound" , "Make louder or fuller" .)