The most common and most likely answer to this crossword clue is the 14 plus 4 letter word I AM FORTUNE’S FOOL
I've seen this crossword clue in The Guardian
I
Â
A
M
Â
F
O
R
T
U
N
E
â
€
™
S
F
O
O
L
Buddy explains!
The straight part
We know that "lover’s lament" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case lover’s lament = i am fortune’s fool.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.