Criticise a mother in straw hat (6)
I believe the answer is:
panama
'straw hat' is the definition.
('panama' can be a synonym of 'straw hat')
'criticise a mother' is the wordplay.
'criticise' becomes 'pan' (informal term meaning to criticise heavily).
'mother' becomes 'ma' (ma is a kind of mother).
'pan'+'a'+'ma'='PANAMA'
'in' is the link.
(Other definitions for panama that I've seen before include "Hat; Central Am. canal" , "country divided by boaters?" , "Central American state" , "Canal zone" , "Central American country" .)