Book in English period (6)
I believe the answer is:
engage
'book' is the definition.
(thesaurus)
'english period' is the wordplay.
'english' becomes 'eng'.
'period' becomes 'age' (I've seen this before).
'eng'+'age'='ENGAGE'
'in' is the link.
(Other definitions for engage that I've seen before include "Employ or get involved in battle" , "start fighting" , "Mesh" , "Hire for work" , "Take on, hire" .)