The most common and most likely answer to this crossword clue is the 7 plus 7 letter word TRICEPS BRACHII
T
R
I
C
E
P
S
B
R
A
C
H
I
I
Buddy explains!
The straight part
We know that "manifestation of armed power" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case manifestation of armed power = triceps brachii.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.