More trouble as head’s dismissed (5)
I believe the answer is:
other
'more' is the definition.
(synonyms)
'trouble as head's dismissed' is the wordplay.
'trouble' becomes 'bother' (synonyms).
'as head's dismissed' means to remove the first letter.
'bother' with its first letter taken off is 'OTHER'.
(Other definitions for other that I've seen before include "Different; alternate" , "Alternative - unrelated" , "One may be significant" , "Different, alternative" , "Different, not the same one or this one" .)