Sailors seizing princess on stage twirling bottom (5)
I believe the answer is:
nadir
'bottom' is the definition.
(I've seen this before)
'sailors seizing princess on stage twirling' is the wordplay.
'sailors' becomes 'RN' (abbreviation for Royal Navy).
'seizing' is an insertion indicator.
'princess on stage' becomes 'ida' (I've seen this before).
'twirling' is a reversal indicator.
'rn' going around 'ida' is 'ridan'.
'ridan' reversed gives 'NADIR'.
(Other definitions for nadir that I've seen before include "most unsuccessful point" , "Drain into the lowest point (5)" , "Drain (anag)" , "It's the depths" , "extremely low position" .)