Military force advanced in long suit (6)
I believe the answer is:
talent
'long suit' is the definition.
(thesaurus)
'military force advanced' is the wordplay.
'military force' becomes 'ta' (I can't explain this - if you can you should give a lot more credence to this answer).
'advanced' becomes 'lent' (money).
'ta'+'lent'='TALENT'
'in' is the link.
Can you help me to learn more?
(Other definitions for talent that I've seen before include "Special aptitude for the old Greek money" , "gift > of Attic gold" , "ancient currency" , "Unit of currency" , "able people" .)