Highly important to survive setback! Stop wasting time (7)
I believe the answer is:
epochal
'highly important' is the definition.
'epochal' can be an answer for 'important' (similar in meaning). I am not certain of the 'highly' bit.
'survive setback stop wasting time' is the wordplay.
'survive' becomes 'cope' (I've seen this before).
'setback' says the letters should be written backwards.
'stop' becomes 'halt' (synonyms).
'wasting' suggests deleting specific letters.
'time' becomes 't' (abbreviation).
'cope' in reverse letter order is 'epoc'.
'halt' with 't' taken away is 'hal'.
'epoc'+'hal'='EPOCHAL'
'to' acts as a link.
Can you help me to learn more?
(Other definitions for epochal that I've seen before include "Of a period in history" , "of a certain age" , "of a particular age" , "Historic" , "Like world-shaking events" .)