Empress turned up when cross (8)
I believe the answer is:
tsaritsa
'empress' is the definition.
(I know that tsaritsa is a type of empress)
'turned up when cross' is the wordplay.
'turned' says the letters should be written backwards.
'up' becomes 'astir' (synonyms).
'when' becomes 'as' (eg 'when I walked' means 'as I walked').
'cross' becomes 'T' (shape).
'astir'+'as'+'t'='astirast'
'astirast' backwards is 'TSARITSA'.
(Other definitions for tsaritsa that I've seen before include "Russian empress" , "ruler's consort" , "Royal lady" .)