Claim tailless river creature returned at a quick pace (10)
I believe the answer is:
allegretto
'claim tailless' is the definition.
I can't judge whether this defines the answer.
'river creature returned at a quick pace' is the wordplay.
'river creature' becomes 'otter' (I've seen this before).
'returned' shows that the letters should be reversed in order.
'at' means one lot of letters go next to another (I've seen this in other clues).
'quick pace' becomes 'lleg' (I am not sure about this - if you are sure you should believe this answer much more).
'otter' written backwards gives 'retto'.
'a'+'lleg'='alleg'
'retto' after 'alleg' is 'ALLEGRETTO'.
Can you help me to learn more?
(Other definitions for allegretto that I've seen before include "with reasonable rapidity" , "quite quickly" , "at a fairly brisk rate" , "somewhat quick" , "Moving fairly briskly (music)" .)