Prune others spreading, indefinite number (7)
I believe the answer is:
shorten
'prune' is the definition.
(thesaurus)
'others spreading indefinite number' is the wordplay.
'spreading' indicates anagramming the letters.
'indefinite number' becomes 'n' (I've seen this in other clues).
'others' with letters rearranged gives 'shorte'.
'shorte'+'n'='SHORTEN'
(Other definitions for shorten that I've seen before include "Abridge" , "Cut back" , "Put extra fat" , "Clip" , "Abbreviate" .)