The most common and most likely answer to this crossword clue is the 6 letter word PEGGED
I've seen this crossword clue in The Guardian
P
E
G
G
E
D
Buddy explains!

The straight part
We know that "Secured" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case secured = pegged.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.
What does PEGGED mean?
PEGGED verb- To fasten using a peg.
- To affix or pin.
- To fix a value or price.
- To narrow the cuff openings of a pair of pants so that the legs take on a peg shape.
- To throw.
- To indicate or ascribe an attribute to. (Assumed to originate from the use of pegs or pins as markers on a bulletin board or a list.)
- To move one's pegs to indicate points scored; to score with a peg.
- To reach or exceed the maximum value on (a scale or gauge).
- (typically in heterosexual contexts) To engage in anal sex by penetrating (one's male partner) with a dildo.
- To keep working hard at something; to peg away.