Recall rising moon blocked by Neptune at the beginning (5)
I believe the answer is:
annul
'recall' is the definition.
(I've seen this before)
'rising moon blocked by neptune at the beginning' is the wordplay.
'rising' says the letters should be written backwards (going up in a down clue).
'moon' becomes 'luna' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'blocked by' means one lot of letters goes inside another (I've seen this in other clues).
'at the beginning' suggests taking the first letters.
The initial letter of 'neptune' is 'n'.
'luna' going around 'n' is 'lunna'.
'lunna' in reverse letter order is 'ANNUL'.
Can you help me to learn more?
(Other definitions for annul that I've seen before include "Declare (a law) invalid" , "Cancel, make void" , "Cancel officially" , "Scrap" , "Make invalid" .)