The nervousness of numbers receiving the charge (7)
I believe the answer is:
tension
'the nervousness' is the definition.
(feeling tense)
'of numbers receiving the charge' is the wordplay.
'of numbers' becomes 'ens' (I can't justify this - if you can you should believe this answer much more).
'receiving' is an insertion indicator (I've seen this in other clues).
'the' becomes 't' (the is pronounced as a 't' sound in some dialects).
'charge' becomes 'ion' (an ion is a charged particle).
't'+'ion'='tion'
'ens' going into 'tion' is 'TENSION'.
Can you help me to learn more?
(Other definitions for tension that I've seen before include "A pulling strain" , "Anxiety" , "Stress, tautness" , "Nervous strain" , "Stretched, uneasy, condition" .)