Equipment heading for armoury in capital (4)
I believe the answer is:
riga
'capital' is the definition.
(capital of Latvia)
'equipment heading for armoury' is the wordplay.
'equipment' becomes 'rig' (rig is a kind of equipment).
'heading for' says to take the initial letters.
The first letter of 'armoury' is 'a'.
'rig'+'a'='RIGA'
'in' acts as a link.
(Other definitions for riga that I've seen before include "A rig in Latvia" , "Baltic capital city" , "European capital" , "trading centre in Latvia" , "Fix a rig up here for the Latvians" .)