German fellow, abstemious type, wearing pair of spectacles (4)
I believe the answer is:
otto
'german fellow' is the definition.
(common German name)
'abstemious type wearing pair of spectacles' is the wordplay.
'abstemious type' becomes 'tt' (abbreviation for teetotaller).
'wearing' means one lot of letters goes inside another.
'pair of spectacles' becomes 'oo' (OO looks like spectacles).
'tt' going inside 'oo' is 'OTTO'.
(Other definitions for otto that I've seen before include "German man's name" , "-- Klemperer, conductor" , "Rose petal oil; Bismarck's name" , "Male German name - a palindrome" , "Palindromic man's name" .)