         \scalebox{0.825}{\begin{forest}
             nice empty nodes,
             for tree={%
                     l sep=2em,
                     s sep=10mm,
                     inner sep=0,
                     calign=fixed edge angles,
                     calign angle=60,
                     l=0}
           [\CP [\lsel{c}{neg} [ {\itshape ní-}]]  [ \thip
                   [\thi [{\itshape -or}]] [ \polp
                         [ \lsel{pol}{neg} [\textit{ól-} \textit{-adar}, roof, name=pol]] [ \tlop
                           [\tlo,name=target]  
                           [\vP  [ \littlev, name=verb] [ 
                                     [{\itshape pro aon nimh sa teach}, roof]
                                        ]]]]]]
           {\draw[->]  (verb)   [out=south west] to [in=south] (target) ;}
           {\draw[->]  (target) [out=south] to [in=south] (pol) ;}
          \end{forest}}