Work out seeing overly large veins engorged initially (5)
I believe the answer is:
solve
'work out' is the definition.
(thesaurus)
'seeing overly large veins engorged initially' is the wordplay.
'initially' suggests taking the first letters.
The first letters of 'seeing overly large veins engorged' is 'SOLVE'.
(Other definitions for solve that I've seen before include "Decipher" , "Unscramble" , "Find an answer to (a problem)" , "Find the answer to a mystery" , "Get the answers" .)