The most common and most likely answer to this crossword clue is the 1 plus 5 plus 3 plus 4 plus 8 letter word A PENNY FOR YOUR THOUGHTS
I've seen this crossword clue in The Times
A
P
E
N
N
Y
F
O
R
Y
O
U
R
T
H
O
U
G
H
T
S
Buddy explains!
The straight part
We know that "What have you in mind?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case what have you in mind? = a penny for your thoughts.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.