Deep in the past, say (7)
I believe the answer is:
intense
'deep' is the definition.
(associated in meaning)
'in the past say' is the wordplay.
'the past say' becomes 'tense' (past tense).
'in'+'tense'='INTENSE'
(Other definitions for intense that I've seen before include "say, description of campers?" , "Strong in quality or degree - perhaps a feeling" , "Teen sin (anag.)" , "Vived, extreme, acute" , "Deeply emotional" .)