Dark at night, spies carrying on with investigations in the end (8)

'dark' is the definition.
(I know that moonless is a more specific form of the attribute dark)

'spies carrying on with investigations in the end' is the wordplay.
'spies' becomes 'moles' (mole is a kind of spy).
'carrying' is an insertion indicator.
'with' is a charade indicator (letters next to each other).
'in the end' suggests the final letters.
The last letter of 'investigations' is 's'.
'moles' placed around 'on' is 'moonles'.
'moonles'+'s'='MOONLESS'

'at night' acts as a link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.

Can you help me to learn more?