The most common and most likely answer to this crossword clue is the 1 plus 5 plus 2 plus 3 plus 3 letter word A TOUCH OF THE SUN
I've seen this crossword clue in The Times
A
T
O
U
C
H
O
F
T
H
E
S
U
N
Buddy explains!
The straight part
We know that "Effect of exposure" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case effect of exposure = a touch of the sun.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.