One’s initial cause of regret about account’s lack of clarity (7)
I believe the answer is:
opacity
'lack of clarity' is the definition.
(I've seen this in another clue)
'one's initial cause of regret about' is the wordplay.
'one' becomes 'a' (a thing is one thing).
'initial' says to take the initial letters.
'of' becomes 'o''.
'regret' becomes 'pity' (I've seen this before).
'about' means one lot of letters goes inside another.
The first letter of 'cause' is 'c'.
'o'+'pity'='opity'
'a'+'c'='ac'
'ac' going inside 'opity' is 'OPACITY'.
'account's' is the link.
I am not very happy about this link. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for opacity that I've seen before include "Obscureness" , "incomprehensible" , "Unclear quality" , "The quality of being impervious to light" , "Lack of transparency" .)