The most common and most likely answer to this crossword clue is the 4 plus 8 letter word JOSE MOURINHO
J
O
S
E
M
O
U
R
I
N
H
O
More clues leading to the result JOSE MOURINHO
Buddy explains!
The straight part
We know that "manager" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case manager = jose mourinho.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.