Regretted giving account earlier to show how it had accumulated (7)
I believe the answer is:
accrued
'show how it had accumulated' is the definition.
I can't judge whether this definition defines the answer.
'regretted giving account earlier' is the wordplay.
'regretted' becomes 'rued' ('rue' can be a synonym of 'regret').
'giving account' becomes 'acc' (I am not sure about the 'giving' bit.).
'earlier' is a charade indicator (letters next to each other).
'rued' after 'acc' is 'ACCRUED'.
'to' acts as a link.
Can you help me to learn more?
(Other definitions for accrued that I've seen before include "Once built-up" , "Accumulated over time" , "Grew or accumulated like interest" .)