A theologian in valley brings cheer (7)
I believe the answer is:
gladden
'cheer' is the definition.
(thesaurus)
'a theologian in valley' is the wordplay.
'theologian' becomes 'dd' (Doctor of Divinity degree).
'in' means one lot of letters goes inside another.
'valley' becomes 'glen' (glen is a kind of valley**).
'a'+'dd'='add'
'add' inserted within 'glen' is 'GLADDEN'.
'brings' is the link.
(Other definitions for gladden that I've seen before include "Make cheerful" , "Make pleased or happy" , "Lift (the heart)" , "Hearten" , "please" .)