Score less than century — that's significant after losing first wicket (6)
I believe the answer is:
eighty
'score' is the definition.
(I have seen 'Several score' mean 'eighty' so perhaps 'score' could also mean 'eighty')
'significant after losing first wicket' is the wordplay.
'significant' becomes 'weighty' (I've seen this before).
'after losing' suggests deleting specific letters.
'first wicket' becomes 'w' (1st letter of 'wicket').
'weighty' with 'w' taken away is 'EIGHTY'.
'less than century that's' is the link.
This may not be right. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for eighty that I've seen before include "Four score" , "4 score" , "Fourscore" , "not many score" , "Number" .)