Chief has drink with engineers (7)
I believe the answer is:
supreme
'chief' is the definition.
(I've seen this in another clue)
'drink with engineers' is the wordplay.
'drink' becomes 'sup' (to sup is to drink).
'with' means one lot of letters go next to another.
'engineers' becomes 'reme' (Royal Electrical and Mechanical Engineers).
'sup'+'reme'='SUPREME'
'has' is the link.
(Other definitions for supreme that I've seen before include "Highest in authority; rich cream sauce (dish)" , "Greatest, highest in excellence" , "topmost level" , "God" , "Paramount" .)