Exclude book jag (4)
I believe the answer is:
barb
'jag' is the definition.
The answer and definition can be both to do with contact as well as being verbs in their base form.
Maybe they are linked in a way I don't understand?
'exclude book' is the wordplay.
'exclude' becomes 'bar' (synonyms).
'book' becomes 'b' (abbreviation for book).
'bar'+'b'='BARB'
Can you help me to learn more?
(Other definitions for barb that I've seen before include "Arrow projection" , "Hurtful witticism - on wire" , "Jag on a hook" , "Arrowhead projection" , "Hook - gibe" .)