Many desert, led by you in the past (9)
I believe the answer is:
thousands
'many' is the definition.
(thesaurus)
'desert led by you in the past' is the wordplay.
'desert' becomes 'sands'.
'led by' says to put letters next to each other.
'you in the past' becomes 'thou' (historical form of 'you').
'sands' after 'thou' is 'THOUSANDS'.
(Other definitions for thousands that I've seen before include "a lot" , "Crowds" , "1000s" , "Dan shouts out at many hundreds" , "large sum?" .)