Sorry - forgot to say Yes to my clue ages ago. As for yours, the letters have certainly helped. Now I know it's PSALTERY - a medieval stringed instrument. PS (the 'afterthought') ALTER (to change) Y (first letter of 'your'). Does the word 'beginning' indicate that the PS should be at the beginning of the word or is it pointing to the letter 'y'?
[Chalky] You are of course correct - and <hidden> The "beginning" was signifying the first letter of "your" i.e. the Y - The order of the parts was I hope implicit in the way the clue was phrased - once you get that "an afterthought" was PS then that would normally precede whatever the text of the PS was, if you see what I mean. <\hidden>
How about another (easy I think) .... a bit nudge, nudge this one ! Secreted when you hear loose woman is satisfied ? (7)
Now - could this one be something like HOARDED? ie. sounds like 'Whore did'? . I will attempt to find a couple of clues to post - I appear to be all 'take' and no 'give'.