Naval force set up before current era (8)
I believe the answer is:
maritime
'naval' is the definition.
(thesaurus)
'force set up before current era' is the wordplay.
'force' becomes 'ram' ('ram' can be a synonym of 'force'**).
'set up' says the letters should be written backwards.
'before' is a charade indicator (letters next to each other).
'current' becomes 'i' (symbol for electric current).
'era' becomes 'time' (I've seen this before).
'ram' backwards is 'mar'.
'mar'+'i'+'time'='MARITIME'
(Other definitions for maritime that I've seen before include "Naval" , "Concerned with the main" , "Found near the sea" , "Of seafaring or shipping" , "Connected to the sea and sea-faring" .)