Spreads top of short pants (6)
I believe the answer is:
shorts
'pants' is the definition.
(shorts is a kind of pants)
'spreads top of short' is the wordplay.
'top' says to take the initial letters.
'of' indicates an anagram (the answer comes from or 'of' the letters).
The first letter of 'spreads' is 's'.
'short' with letters rearranged gives 'horts'.
's'+'horts'='SHORTS'
(Other definitions for shorts that I've seen before include "Summer trousers" , "Garment" , "Reduced trousers" , "Item of clothing; drinks of spirit" , "Trousers that end at or above the knee" .)