Those people will be tense initially, on edge (4)
I believe the answer is:
them
'those people' is the definition.
(I've seen this before)
'tense initially on edge' is the wordplay.
'initially' suggests taking the first letters.
'on' means one lot of letters go next to another.
'edge' becomes 'hem' (I've seen this before**).
The initial letter of 'tense' is 't'.
't'+'hem'='THEM'
'will be' is the link.
(Other definitions for them that I've seen before include "Perhaps, the Opposition" , "(To/from) those people" , "Those people (as object)" , "people objectively" , "... in another case, they" .)