Secure bananas in boat (6)
I believe the answer is:
obtain
'secure' is the definition.
(synonyms)
'bananas in boat' is the wordplay.
'bananas' indicates an anagram (informal term for mad).
'in'+'boat'='inboat'
'inboat' anagrammed gives 'OBTAIN'.
(Other definitions for obtain that I've seen before include "Acquire, secure" , "Gain possession of" , "Get or receive" , "Get one's hands on" , "Take possession of" .)