English firm receiving tax returns in standard interval (6)
I believe the answer is:
octave
'standard interval' is the definition.
'octave' can be an answer for 'interval' (musical interval). I am not sure about the 'standard' bit.
'english firm receiving tax returns' is the wordplay.
'english' becomes 'E' (abbreviation).
'firm' becomes 'co' (a firm is a company).
'receiving' indicates putting letters inside.
'tax' becomes 'VAT' (Value-Added Tax).
'returns' is a reversal indicator.
'e'+'co'='eco'
'eco' enclosing 'vat' is 'evatco'.
'evatco' reversed gives 'OCTAVE'.
'in' acts as a link.
Can you help me to learn more?
(Other definitions for octave that I've seen before include "Series of eight consecutive musical notes" , "Musical term - set of eight" , "Musical interval of eight notes" , "Eight consecutive notes on music scale" , "Musical interval of eight tones" .)