Complaint from me before son gets in beers (7)
I believe the answer is:
measles
'complaint' is the definition.
(measles is a kind of health problem)
'me before son gets in beers' is the wordplay.
'before' means one lot of letters go next to another.
'son' becomes 's' (genealogical abbreviation for son).
'gets in' means one lot of letters goes inside another.
'beers' becomes 'ales' (I've seen this before).
's' inserted inside 'ales' is 'asles'.
'me'+'asles'='MEASLES'
'from' is the link.
(Other definitions for measles that I've seen before include "Childhood viral disease" , "I appear as 8 [RASH]" , "Morbilli is technical term for this illness" , "Rubeola" , "Children's disease with red spots" .)