Suppose wife has lost faith (4,2)
I believe the answer is:
what if
'suppose' is the definition.
(both might be said before a hypothesis)
'wife has lost faith' is the wordplay.
'wife' becomes 'w' (abbreviation).
'has' says to put letters next to each other.
'lost' indicates an anagram.
'faith' with letters rearranged gives 'hatif'.
'w'+'hatif'='WHAT IF'
(Other definitions for what if that I've seen before include "Hypothetical situation" , "Suppose" , "How would it be when (something happened?)" , "How would things go when" , "hypothetical question" .)