Cry when wife has trouble (4)
I believe the answer is:
wail
'cry' is the definition.
(I know that wail is a type of complaint)
'wife has trouble' is the wordplay.
'wife' becomes 'w' (abbreviation).
'has' is a charade indicator (letters next to each other).
'trouble' becomes 'ail' (synonyms).
'w'+'ail'='WAIL'
'when' acts as a link.
(Other definitions for wail that I've seen before include "(Make a) plaintive cry" , "Mournful cry" , "Cry of lament" , "Utter a long sad cry" , "Cry of grief" .)