Knight getting help, bringing in a nymph (5)
I believe the answer is:
naiad
'nymph' is the definition.
(naiad is a kind of nymph)
'knight getting help bringing in a' is the wordplay.
'knight' becomes 'n' (chess).
'getting' says to put letters next to each other.
'help' becomes 'aid' ('aid' can be a synonym of 'help'**).
'bringing in' is an insertion indicator.
'aid' enclosing 'a' is 'aiad'.
'n'+'aiad'='NAIAD'
(Other definitions for naiad that I've seen before include "Classic spirit" , "watery spirit" , "Aquatic larva of a dragonfly" , "Nymph of lakes, springs and rivers" , "divine female figure" .)