Foreign currency invested in new name for nerve cell (6)
I believe the answer is:
neuron
'nerve cell' is the definition.
('neuron' can be a synonym of 'nerve cell')
'foreign currency invested in new name' is the wordplay.
'foreign currency' becomes 'euro' (I've seen this before).
'invested in' is an insertion indicator.
'new' becomes 'n'.
'name' becomes 'n' (common abbreviation e.g. on forms).
'n'+'n'='nn'
'euro' put within 'nn' is 'NEURON'.
'for' is the link.
(Other definitions for neuron that I've seen before include "Cell that conducts nerve impulses" , "It transmits nerve impulses" , "Part of one's nervous system" , "Nerve impulse cell" , "Transmitter of nerve impulses" .)