Beloved daughter departs for an unknown period (4)
I believe the answer is:
year
'period' is the definition.
(I know that year is a type of period)
'beloved daughter departs for an unknown' is the wordplay.
I cannot quite see how this works, but
'an' could be 'a' and 'a' is found within the answer.
'unknown' could be 'y' (algebra) and 'y' is located in the answer.
The remaining letters 'er' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for year that I've seen before include "One orbit round the sun" , "365 or 366 days" , "26 fortnights" , "1% of a century" , "Two semesters" .)