In moody period, king prowls around (6)
I believe the answer is:
skulks
'prowls around' is the definition.
(to skulk is to prowl or creep around)
'in moody period king' is the wordplay.
'in' is an insertion indicator.
'moody period' becomes 'sulks' (the sulks can mean a period of sulking).
'king' becomes 'K' (abbreviation for king in chess).
'sulks' enclosing 'k' is 'SKULKS'.
(Other definitions for skulks that I've seen before include "Loiters and moves stealthily" , "Hides or lurks, planning mischief" , "Loiters stealthily, lurks" , "Lurks, sneaks, prowls" .)