Struggle up in the fourth gift floor (5)
I believe the answer is:
fight
'struggle' is the definition.
(I know that struggle can be written as fight)
'up in the fourth gift floor' is the wordplay.
'up' says the letters should be written backwards (in down clue: letters go upwards).
'in' says the answer is hidden in the clue.
'thgif' is hidden in the letters of 'fourth gift floor'.
'thgif' back-to-front is 'FIGHT'.
(Other definitions for fight that I've seen before include "Box" , "Attack or engage in combat" , "Scrap" , "Spar" , "Campaign against - quarrel" .)