Make an inquiry while king (3)
I believe the answer is:
ask
'make an inquiry' is the definition.
(I've seen this in another clue)
'while king' is the wordplay.
'while' becomes 'as' (eg 'while I walked' means 'as I walked').
'king' becomes 'K' (chess abbreviation).
'as'+'k'='ASK'
(Other definitions for ask that I've seen before include "Make enquiry" , "Issue invitations" , "Inquire" , "Enquire" , "Put a question" .)