Close down before time, almost (6)
I believe the answer is:
Here is my best explanation:
'close' is the definition.
'down before time almost' is the subsidiary indication.
'down' becomes 'dn'.
'before time' becomes 'early' (I've seen this before).
'almost' means to remove the first letter.
'dnearly' with its initial letter removed is 'nearly'.
(Other definitions for nearly that I've seen before include "Well-nigh", "Not quite, almost", "More or less", "Almost, not quite", "Give out a bright light" and "Almost, well-nigh".)