Absent-minded sergeant losing material on holiday (6)
I believe the answer is:
vacant
'absent-minded' is the definition.
(thesaurus)
'material on holiday' is the wordplay.
'material' becomes 'ant' (I can't justify this - if you can you should give a lot more credence to this answer).
'on' says to put letters next to each other.
'holiday' becomes 'vac' (abbreviation for vacation).
'ant' put after 'vac' is 'VACANT'.
'sergeant losing' acts as a link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for vacant that I've seen before include "Empty - stupid" , "Not filled, job or house" , "Empty, not occupied" , "Without an occupant or incumbent" , "available" .)