Father of 7 exposed new master (5)
I believe the answer is:
learn
'master' is the definition.
(thesaurus)
'father of 7 exposed new' is the wordplay.
'father of 7' becomes 'lear' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'exposed' means to look at the middle letters (outside letters removed).
'new' becomes 'brannew' ('bran-new' can be similar in meaning to 'new').
The middle of 'brannew' is 'n'.
'lear'+'n'='LEARN'
(Other definitions for learn that I've seen before include "Ascertain" , "Gain knowledge or skill" , "Hear - memorise" , "Acquire information" , "Pick up" .)