Tracking device put in enclosure beside government building (8)
I believe the answer is:
pentagon
'government building' is the definition.
'Pentagon' can be an answer for 'building' (Pentagon is an example). I'm not certain of the 'government' bit.
'tracking device put in enclosure beside' is the wordplay.
'tracking device' becomes 'tag' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'put in' means one lot of letters goes inside another (back).
'enclosure' becomes 'pen' (pen is a kind of enclosure).
'beside' becomes 'on'.
'pen'+'on'='penon'
'tag' placed within 'penon' is 'PENTAGON'.
Can you help me to learn more?
(Other definitions for pentagon that I've seen before include "rectilineal figure" , "US building of high security" , "Headquarters of USA Department of Defence" , "military leadership" , "government HQ abroad" .)