Detain scout roughly and leave far behind (11)
I believe the answer is:
outdistance
'leave far behind' is the definition.
(I've seen this before)
'detain scout roughly' is the wordplay.
'roughly' is an anagram indicator.
'detain'+'scout'='detainscout'
'detainscout' with letters rearranged gives 'OUTDISTANCE'.
'and' is the link.
(Other definitions for outdistance that I've seen before include "Travel further than" , "Leave (someone) far behind" .)