Second city in Florida mostly rugged countryside (8)
I believe the answer is:
moorland
'rugged countryside' is the definition.
'second city in florida mostly' is the wordplay.
'second' becomes 'mo' (both are short periods of time).
'city in florida' becomes 'orlando' (I've seen this before).
'mostly' means to remove the last letter.
'orlando' with its last letter taken off is 'orland'.
'mo'+'orland'='MOORLAND'
(Other definitions for moorland that I've seen before include "Tract of open shrubby ground" , "Extensive tract of hill country" , "Wild area of countryside (usually with heather)" , "Baskerville Hall, for example, is found" , "Extensive upland tract" .)