Sounds feeble for seven days (4)
I believe the answer is:
week
'seven days' is the definition.
(I've seen this in another clue)
'sounds feeble' is the wordplay.
'sounds' shows a homophone (sound like).
'feeble' becomes 'weak' (similar in meaning).
'weak' is a homophone of 'WEEK'.
'for' acts as a link.
(Other definitions for week that I've seen before include "Calendar period" , "Period of time; sounds like feeble" , "A long time in politics?" , "Seven days" , "Seven day period" .)