The most common and most likely answer to this crossword clue is the 4 plus 7 plus 8 letter word PULL ONESELF TOGETHER
I've seen this crossword clue in The Guardian
P
U
L
L
O
N
E
S
E
L
F
T
O
G
E
T
H
E
R
Buddy explains!
The straight part
We know that "regain control" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case regain control = pull oneself together.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.