Where one finds nuns hiding knight? That is awkward (12)
I believe the answer is:
inconvenient
'awkward' is the definition.
(similar in meaning)
'where one finds nuns hiding knight? that is' is the wordplay.
'where one finds nuns' becomes 'in convent' (nuns live in convents).
'hiding' means one lot of letters goes inside another.
'knight?' becomes 'N' (chess abbreviation).
'that is' becomes 'ie' (short for Latin 'id est', 'that is').
'n'+'ie'='nie'
'inconvent' enclosing 'nie' is 'INCONVENIENT'.
(Other definitions for inconvenient that I've seen before include "Troublesome" , "Causing slight difficulty" , "Ill-timed" , "Causing difficulties" , "Awkward" .)