Crossword Genius

Charge then drop back, dispersed by this? (4,3)

Ross

I believe the answer is:

tear gas

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'dispersed by this?' is the definition.
The definition suggests a singular noun which matches the answer.

'charge then drop back' is the wordplay.
'charge then' becomes 'tear' (synonyms. I am not sure about the 'then' bit.).
'drop' becomes 'sag' (sagging is a kind of dropping).
'back' shows that the letters should be reversed in order.
'sag' backwards is 'gas'.
'tear'+'gas'='TEAR-GAS'

Can you help me to learn more?

(Other definitions for tear gas that I've seen before include "'It can be used to disperse crowds (4,3)'" , "Crowd disperser" , "Irritating stuff" , "Police weapon" , "Riot-control weapon" .)

I've seen this clue in The Times.
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