In all probability, Robin of Loxley and his ilk lie outlandishly. (10)
I believe the answer is:
likelihood
'in all probability' is the definition.
(I've seen this before)
'robin of loxley and his ilk lie outlandishly' is the wordplay.
I cannot really see how this works, but
'robin' could be 'hood' (I've seen this in other clues) and 'hood' is found within the answer.
an anagram of 'ilk' is 'lik' which is within the answer.
an anagram of 'lie' is 'eli' which is within the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Another definition for likelihood that I've seen is " Probability".)