Tramp sees a sharp increase (4)
I believe the answer is:
hike
I believe this is a double definition.
'tramp' is the first definition.
(I know that tramp can be written as hike)
'a sharp increase' is the second definition.
(I've seen this in another clue)
'sees' acts as a link.
(Other definitions for hike that I've seen before include "Increase cost" , "Jack" , "Long walk - sharp increase" , "Tramp" , "physical exercise" .)