Test facing men over period of time in transport (10)
I believe the answer is:
motorcycle
'transport' is the definition.
(motorcycle is a kind of transport)
'test facing men over period of time' is the wordplay.
'test' becomes 'mot'.
'facing' is a charade indicator (letters next to each other).
'men' becomes 'or' (I've seen this in other clues).
'over' is a charade indicator (letters next to each other).
'period of time' becomes 'cycle' (cycle is a kind of period of time**).
'mot'+'or'+'cycle'='MOTORCYCLE'
'in' acts as a link.
(Other definitions for motorcycle that I've seen before include "Petrol-driven two-wheeler" , "Two-wheeled vehicle" , "Triumph for rider, perhaps" , "It's used for scrambling" , "transport" .)