The most common and most likely answer to this crossword clue is the 16 letter word POST-REFORMATION
I've seen this crossword clue in Independent
P
O
S
T
-
R
E
F
O
R
M
A
T
I
O
N
Buddy explains!
The straight part
We know that "&lit-ish – period (of history)" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case &lit-ish – period (of history) = post-reformation.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.