Weak with flu, shaking, unable to sleep (7)
I believe the answer is:
wakeful
'unable to sleep' is the definition.
(I've seen this in another clue)
'weak with flu shaking' is the wordplay.
'with' means one lot of letters go next to another.
'shaking' indicates anagramming the letters.
'weak' put after 'flu' is 'fluweak'.
'fluweak' is an anagram of 'WAKEFUL'.
(Other definitions for wakeful that I've seen before include "Not sleepy" , "Alert, vigilant" , "Unable to sleep" , "Not getting off" .)