A lot'll back daughter, taking everything into account (3,4)
I believe the answer is:
all told
'taking everything into account' is the definition.
(I've seen this before)
'a lot'll back daughter' is the wordplay.
'back' says the letters should be written in reverse.
'daughter' becomes 'd'.
'lotll' backwards is 'lltol'.
'a'+'lltol'+'d'='ALL TOLD'
(Other definitions for all told that I've seen before include "With everything or everyone taken into account" , "book reading's finished?" , "In total" , "Nothing missed out" , "Everyone informed" .)