Weight rose rapidly up, partly in place of relaxing (6)
I believe the answer is:
'place of relaxing' is the definition.
(eg a spa resort)
'weight rose rapidly up partly' is the wordplay.
'partly' indicates a hidden word (part of the clue is used).
'up' is a reversal indicator (in down clue: letters go upwards).
'troser' is hidden within 'weight rose rapidly'.
'troser' back-to-front is 'RESORT'.
'in' acts as a link.
(Other definitions for resort that I've seen before include "Holiday destination" , "Watering-place" , "Place many go to" , "Where one may stay in hotel" , "place for holidaymakers to go to" .)