Is Queen Rat travelling on horseback? (10)
I believe the answer is:
equestrian
'on horseback?' is the definition.
(I've seen this before)
'is queen rat travelling' is the wordplay.
'travelling' is an anagram indicator.
'is'+'queen'+'rat'='isqueenrat'
'isqueenrat' anagrammed gives 'EQUESTRIAN'.
(Other definitions for equestrian that I've seen before include "Horseman" , "Horse-rider" , "Person on horseback" , "Jockey" , "Relating to horse riding" .)