Quantity sent there (5)
I believe the answer is:
three
'quantity' is the definition.
(I know that three is a near-square prime)
'sent there' is the wordplay.
'sent' is an anagram indicator (send can mean to excite or stimulate).
'there' anagrammed gives 'THREE'.
(Other definitions for three that I've seen before include "Number constituting a crowd?" , "Number of Furies or Norns" , "Number of Dumas's musketeers" , "Square root of nine" , "So many 12s today" .)