Tense dad, holy person without blemish (4,7)
I believe the answer is:
past perfect
'tense' is the definition.
(past perfect is a kind of tense)
'dad holy person without blemish' is the wordplay.
'dad' becomes 'pa' (both can mean one's father).
'holy person' becomes 'st' (short for saint).
'without blemish' becomes 'perfect' (I've seen this before).
'pa'+'st'+'perfect'='PAST PERFECT'
(Other definitions for past perfect that I've seen before include "No skeletons in the cupboard" , "one tense" , "had rattled, for example?" , "Extreme view about the good old days" , "Tersely stated nostalgic illusion" .)