He'll have halved the danger by the end of February (5)
I believe the answer is:
gerry
'he'll' is the definition.
The definition suggests a singular noun which matches the answer.
'halved the danger by the end of february' is the wordplay.
'halved' suggests halving the letters.
'by' means one lot of letters go next to another.
'the end of february' becomes 'ry' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'danger' with half the letters taken is 'ger'.
'ger'+'ry'='GERRY'
'have' acts as a link.
Can you help me to learn more?
(Other definitions for gerry that I've seen before include "- and the Pacemakers, 1960s pop group" , "-- Mulligan, US jazz saxophonist" .)