Confidential talk foolishly interrupted by a drip (7)
I believe the answer is:
private
'confidential' is the definition.
(similar in meaning)
'talk foolishly interrupted by a drip' is the wordplay.
'talk foolishly' becomes 'prate' (to prate is to talk nonsense).
'interrupted by' means one lot of letters goes inside another.
'a drip' becomes 'IV' (intravenous drip).
'prate' placed around 'iv' is 'PRIVATE'.
(Other definitions for private that I've seen before include "Secret - soldier of the lowest rank" , "Not open to scrutiny" , "Lowest rank of enlisted person" , "Not openly shared" , "Secret, not public" .)