Arrange loads around the nerve centre of the back (6)
I believe the answer is:
dorsal
'of the back' is the definition.
(I've seen this before)
'arrange loads around the nerve centre' is the wordplay.
'arrange' is an anagram indicator.
'around' means one lot of letters goes inside another.
'centre' means to look at the middle letters.
The middle letter of 'nerve' is 'r'.
'loads' is an anagram of 'dosal'.
'dosal' enclosing 'r' is 'DORSAL'.
(Other definitions for dorsal that I've seen before include "(Of fin) on upper side" , "'On the back, a fin on a fish perhaps (6)'" , "Kind of fin" , "Fin on the back of marine vertebrates" , "On the back, fin on a fish say" .)