Support a parent but dont talk about it (4,3)
I believe the answer is:
keep mum
'dont talk about it' is the definition.
I can't judge whether this defines the answer.
'support a parent' is the wordplay.
'support' becomes 'keep' (synonyms).
'a parent' becomes 'mum' (mum is a kind of parent).
'keep'+'mum'='KEEP MUM'
'but' is the link.
Can you help me to learn more?
(Other definitions for keep mum that I've seen before include "Stay silent" , "(don't mention it)" , "Remain silent" , "Don't tell a soul" .)