The most common and most likely answer to this crossword clue is the 2 plus 4 plus 1 plus 4 letter word ON SHOW - ON'S
I've seen this crossword clue in The Times
O
N
S
H
O
W
-
O
N
'
S
Buddy explains!
The straight part
We know that "hardly secret" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case hardly secret = on show - on's.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.