Stationed last of troops in turbulent Rio Grande (10)

'stationed' is the definition.
(garrisoning is a kind of stationing)

'last of troops in turbulent rio grande' is the wordplay.
'last of' indicates one should take the final letters.
'in' indicates putting letters inside.
'turbulent' indicates anagramming the letters.
The last letter of 'troops' is 's'.
'rio'+'grande'='riogrande'
'riogrande' with letters rearranged gives 'garrioned'.
's' inserted within 'garrioned' is 'GARRISONED'.