Initially having appeared, lax, vague even, share equally (5)
I believe the answer is:
halve
'share equally' is the definition.
(split into two halves)
'initially having appeared lax vague even' is the wordplay.
'initially' suggests taking the first letters.
The first letters of 'having appeared lax vague even' is 'HALVE'.
(Other definitions for halve that I've seen before include "Cut into two equal portions" , "Reduce by a factor of two" , "Divide equally between two" , "Divide into two equal parts" , "split with another" .)