Station underground with no opening in cold period (5)
I believe the answer is:
inter
'station underground' is the definition.
(to inter is to position underground)
'with no opening in cold period' is the wordplay.
'with no opening in' means to remove the first letter.
'cold period' becomes 'winter' (coldest season).
'winter' with its first letter taken away is 'INTER'.
(Other definitions for inter that I've seen before include "Inhume" , "promoting cessation" , "somewhere between ..." , "Place in ground" , "Settle in ground" .)