Emphasise that electricity takes very little money! (6)
I believe the answer is:
accent
'emphasise' is the definition.
(synonyms)
'electricity takes very little money' is the wordplay.
'electricity' becomes 'AC' (AC is an example).
'takes' means one lot of letters go next to another.
'very little money' becomes 'cent' (eg hundredth of a dollar).
'ac'+'cent'='ACCENT'
'that' is the link.
(Other definitions for accent that I've seen before include "Stress - manner of speech" , "Particular emphasis" , "Distinctive way of pronouncing words" , "Regional speech characteristic" , "Emphasis on syllabus or word" .)