Dries up, accompanied by the Queen on last of duties (7)
I believe the answer is:
withers
'dries up' is the definition.
(I've seen this before)
'accompanied by the queen on last of duties' is the wordplay.
'accompanied by' becomes 'with' (I've seen this before).
'the queen on last of duties' becomes 'ers' (I can't justify this - if you can you should give a lot more credence to this answer).
'with'+'ers'='WITHERS'
Can you help me to learn more?
(Other definitions for withers that I've seen before include "droops?" , "Back section of a horse" , "Languishes; part of horse near shoulder-blades" , "dries up" , "fades" .)