Characters detained in Slovakian cells (3)
I believe the answer is:
ova
'cells' is the definition.
(ovum is a kind of cell)
'characters detained in slovakian' is the wordplay.
'characters detained in' says the answer is hidden in the clue (some letters or characters from the clue).
'OVA' is hidden within 'slovakian'.
(Other definitions for ova that I've seen before include "targets for male seed?" , "Latin egg-cells" , "Multiple Latin eggs" , "Release of women" , "Female egg cells" .)