A hand needed to secure second military bar (5)
I believe the answer is:
clasp
'military bar' is the definition.
(bar on a military medal)
'a hand needed to secure second' is the wordplay.
'a hand' becomes 'clap' (both can mean a round of applause).
'needed to secure' indicates putting letters inside (insert letters are secured or held).
'second' becomes 's' (common abbreviation).
'clap' placed around 's' is 'CLASP'.
(Other definitions for clasp that I've seen before include "Grip firmly" , "Hug" , "Handshake or fastening device" , "Fastening - firm grip" , "bosom" .)