One must do it to survive (7)
I believe the answer is:
outlive
'survive' is the definition.
(I know that survive can be written as outlive)
'one must do it' is the wordplay.
I cannot quite see how this works, but
'one' could be 'i' (Roman numeral) and 'i' is found within the answer.
'do' could be 'ut' (synonyms) and 'ut' is found within the answer.
'it' could be 'e' ('e' can mean 'electronic' which is similar to 'IT') and 'e' is located in the answer.
This explanation may well be incorrect...
'to' acts as a link.
Can you help me to learn more?
(Other definitions for outlive that I've seen before include "Die after" , "Survive longer than" , "Survive beyond (another)" , "weather" , "Go on longer than" .)