Provide very strong soldiers before the day's over (6)
I believe the answer is:
afford
'provide' is the definition.
(affording is a kind of providing)
'strong soldiers before the day's over' is the wordplay.
'strong' becomes 'ff'.
'soldiers' becomes 'OR' (Other Ranks).
'before' means one lot of letters go next to another.
'the day's' becomes 'ad' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'over' means one lot of letters goes inside another.
'ff'+'or'='ffor'
'ffor' inserted within 'ad' is 'AFFORD'.
'very' acts as a link.
Can you help me to learn more?
(Other definitions for afford that I've seen before include "Have enough money to pay for" , "Able to bear the expense" , "Be able to buy" , "Yield!" , "Able to bear the cost of" .)