Waver, and depart carrying infirm (9)
I believe the answer is:
vacillate
'waver' is the definition.
(I know that waver can be written as vacillate)
'depart carrying infirm' is the wordplay.
'depart' becomes 'vacate' (I can't justify this - if you can you should give a lot more credence to this answer).
'carrying' means one lot of letters goes inside another.
'infirm' becomes 'ill' (similar in meaning).
'vacate' going around 'ill' is 'VACILLATE'.
'and' is the link.
Can you help me to learn more?
(Other definitions for vacillate that I've seen before include "Keep changing one's mind" , "Be unsteady" , "Shilly-shally" , "Be in two minds" , "indecisive" .)