Some retired female’s particular niche (4)
I believe the answer is:
'niche' is the definition.
(apse is a kind of niche)
'some retired female's particular' is the wordplay.
'retired' says the letters should be written backwards.
'some' says the answer is hidden in the clue (some of the parts of the word are used).
'espa' is hidden in the letters of 'females particular'.
'espa' reversed gives 'APSE'.
(Other definitions for apse that I've seen before include "where praetor sat" , "may be seen in church!" , "Recess at east end of church" , "Recess in church wall" , "Church recess with domed or arched roof" .)