Saying little historian's son leaves navy (8)
I believe the answer is:
taciturn
'saying little' is the definition.
(I've seen this before)
'historian's son leaves navy' is the wordplay.
'historian's' becomes 'tacituss' (Roman historian).
'son' becomes 'ss' (I've seen this in other clues).
'leaves' indicates named letters should be taken away.
'navy' becomes 'rn' (abbreviation for Royal Navy).
'tacituss' with 'ss' taken away is 'tacitu'.
'tacitu'+'rn'='TACITURN'
(Other definitions for taciturn that I've seen before include "Talking little" , "Not inclined to conversation" , "Disinclined towards conversation" , "Tending to silence" , "Without saying much" .)