Maybe another solution could be to reduce the clef size, e.g.:
\version "2.20.0"
\paper {
line-width = 50
}
\layout {
indent = 0
system-count = 1
}
<<
\new Staff { R2.*3 c''8 8 8 8 8 8 8 8 8 8 8 8 }
\new Staff { R2. c''4 r r c'' r r r e'' r r d'' r }
\new Staff {
\clef F \time 3/4 R2.*3
\clef G g4 r r g r r
\once\override Staff.Clef.X-extent = #'(-2 . 1)
%\once\override Staff.Clef.space-alist = #'((staff-bar extra-space . 5))
%% or:
\once\override Staff.Clef.space-alist = #'((staff-bar minimum-space . 2))
\once\set Staff.fontSize = #-1
\clef F
}
>>
Pierre