National Guards about to perform specific steps (5)
I believe the answer is:
dance
'steps' is the definition.
('dance step' can be a synonym of 'step')
'national guards about' is the wordplay.
'national' becomes 'n' (abbreviation listed in Chambers).
'guards' becomes 'dace' (I am not sure about this - if you are sure you should believe this answer much more).
'about' means one lot of letters goes inside another.
'n' inserted into 'dace' is 'DANCE'.
'to perform specific' acts as a link.
This may not be right. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for dance that I've seen before include "See 4" , "Move(ment) to music" , "social event" , "Eg, foxtrot or tango" , "Eg, waltz, foxtrot" .)