Bird for one: about time (5)
I believe the answer is:
Here is my best explanation:
'bird' is the definition.
(egret is a kind of bird)
'for one about time' is the subsidiary indication.
'for one' becomes 'eg' (I've seen this in other clues).
'about' becomes 're' (common abbreviation for 'with reference to').
'time' becomes 't'.
(Other definitions for egret that I've seen before include "White wading bird", "Long-plumed heron", "Bird eating fish", "white fish eater", "White wading-bird", "Kind of heron with long white feathers", "Stork-like bird", "Flier", "Type of heron" and "White-plumed wader".)