I've made a mistake over love note at end of e-mail, perhaps (4)
I believe the answer is:
oops
'i've made a mistake' is the definition.
(oops may be said to acknowledge a mistake)
'love note at end of e-mail perhaps' is the wordplay.
'love' becomes 'o' (love means zero in tennis).
'note' becomes 'PS' (a PS or postscript in a letter).
'at end of' says to put letters next to each other (some letters go at the end of others).
'e-mail perhaps' becomes 'o' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'ps' after 'o' is 'ops'.
'o'+'ops'='OOPS'
'over' acts as a link.
Can you help me to learn more?
(Other definitions for oops that I've seen before include "Exclamation on making a minor mistake" , "- - -a-daisy" , "The sound of stupidity" , "Exclamation on making minor error" , "I've messed up" .)