Follow us up in an absolute sense (6)
I believe the answer is:
pursue
'follow' is the definition.
(to pursue is to follow or chase)
'us up in an absolute sense' is the wordplay.
'up' indicates anagramming the letters (letters get chucked up).
'in' indicates putting letters inside.
'an absolute sense' becomes 'pure' (I am not sure about this - if you are sure you should believe this answer much more).
'us' is an anagram of 'su'.
'su' put inside 'pure' is 'PURSUE'.
Can you help me to learn more?
(Other definitions for pursue that I've seen before include "Follow up on or go after" , "Dog" , "Engage in or chase after" , "Follow, chase" , "Chase, run after" .)