Pioneering males in trouble (7)
I believe the answer is:
seminal
'pioneering' is the definition.
(I've seen this in another clue)
'males in trouble' is the wordplay.
'trouble' indicates an anagram.
'males'+'in'='malesin'
'malesin' is an anagram of 'SEMINAL'.
(Other definitions for seminal that I've seen before include "Very important, original" , "Menials giving rise to new beginnings" , "Of seed, or giving rise to new developments" , "Of beginnings or early developments" , "Major" .)