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' is an anagram indicator (letters get chucked up).
'in' means one lot of letters goes inside another.
'an absolute sense' becomes 'pure' (I can't justify this - if you can you should give a lot more credence to this answer).
'us' anagrammed gives 'su'.
'su' going 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" .)