Sure, troop has old look (5)
I believe the answer is:
retro
'old look' is the definition.
The definition suggests a singular noun which matches the answer.
'sure troop has' is the wordplay.
'has' indicates a hidden word.
'RETRO' is hidden in the letters of 'sure troop'.
Can you help me to learn more?
(Other definitions for retro that I've seen before include "Imitative of a style from the recent past" , "Of a past time" , "Old-fashioned style" , "Describes the style of an earlier time, in short" , "Prefix for old-style" .)