Embrace German repeatedly downing stein in secret (6-6)
I believe the answer is:
hugger-mugger
'in secret' is the definition.
(I've seen this before)
'embrace german repeatedly downing stein' is the wordplay.
'embrace' becomes 'hug' (synonyms).
'german' becomes 'ger' (abbreviation).
'repeatedly' says to double the letters.
'downing' is an insertion indicator (to down food or drink is to swallow it quickly).
'stein' becomes 'mug' (a stein is a mug-like vessel).
'ger' doubled is 'gerger'.
'gerger' placed around 'mug' is 'germugger'.
'hug'+'germugger'='HUGGER-MUGGER'
(Other definitions for hugger-mugger that I've seen before include "In secret - disorderly ..." , "(In) confusion" , "In utter disorder - in secret" .)