The French female admitting mistake, largely shown up – seriously! (3,4)
I believe the answer is:
for real
'seriously' is the definition.
(thesaurus)
'the french female admitting mistake largely shown up' is the wordplay.
'the french female' becomes 'fal' (I can't justify this - if you can you should give a lot more credence to this answer).
'admitting' indicates putting letters inside (admit can mean to welcome in or accept).
'mistake' becomes 'error' (synonyms).
'largely' means to remove the last letter.
'shown up' says the letters should be written in reverse.
'error' with its last letter removed is 'erro'.
'erro' backwards is 'orre'.
'fal' placed around 'orre' is 'FOR REAL'.
Can you help me to learn more?
(Other definitions for for real that I've seen before include "Serious" , "certainly" .)