Recall climbing in trek overseas (5)
I believe the answer is:
evoke
'recall' is the definition.
(I've seen this before)
'climbing in trek overseas' is the wordplay.
'climbing' shows that the letters should be reversed in order (in a down clue, letters climb up).
'in' says the answer is hidden in the clue.
'ekove' can be found hidden inside 'trek overseas'.
'ekove' backwards is 'EVOKE'.
(Other definitions for evoke that I've seen before include "Call up; elicit" , "Elicit (a response)" , "Arouse" , "Recall" , "Call forth (a response)" .)