Send an aid in spirit (5)
I believe the answer is:
naiad
'spirit' is the definition.
(I've seen this before)
'send an aid' is the wordplay.
'send' is an anagram indicator (I've seen 'sent' mean this (send can mean to excite or stimulate)).
'an'+'aid'='anaid'
'anaid' is an anagram of 'NAIAD'.
'in' is the link.
(Other definitions for naiad that I've seen before include "Diana (anag.)" , "River nymph" , "Fabulous spring being" , "divine female figure" , "Mythological water-nymph" .)