German sues about estimate (5)
I believe the answer is:
guess
'estimate' is the definition.
(I know that estimate can be written as guess)
'german sues about' is the wordplay.
'german' becomes 'g' (abbreviation).
'about' indicates anagramming the letters.
'sues' is an anagram of 'uess'.
'g'+'uess'='GUESS'
(Other definitions for guess that I've seen before include "Reckon" , "Take a stab at the answer" , "Speculation" , "Estimate, supposition" , "Estimate; suppose" .)