Running down info about militancy, ignored by clubs (10)
I believe the answer is:
negativism
'running down' is the definition.
'info about militancy ignored by clubs' is the wordplay.
'info' becomes 'gen' (gen is a kind of info).
'about' says the letters should be written in reverse.
'militancy' becomes 'activism'.
'ignored by' indicates named letters should be taken away.
'clubs' becomes 'c' (abbreviation used in card games such as bridge).
'gen' reversed gives 'neg'.
'activism' with 'c' taken out is 'ativism'.
'neg'+'ativism'='NEGATIVISM'
(Another definition for negativism that I've seen is " Being very critical".)