Find unfinished unit very limited and oddly small across-the-board (9)
I believe the answer is:
universal
'across-the-board' is the definition.
(thesaurus)
'find unfinished unit very limited and oddly small' is the wordplay.
'find' is an anagram indicator.
'unfinished' means to remove the last letter.
'limited' means to remove the last letter (a limited or incomplete form of the word).
'and' is a charade indicator (letters next to each other).
'oddly' means one should take alternating letters (letters in the odd-numbered positions are used).
The alternate letters of 'small' are 'sal'.
'unit' with its final letter taken away is 'uni'.
'very' with its last letter taken away is 'ver'.
'uni'+'ver'='univer'
'univer' put after 'sal' is 'saluniver'.
'saluniver' is an anagram of 'UNIVERSAL'.
(Other definitions for universal that I've seen before include "Common" , "Widespread, worldwide" , "Without exception" , "Applying everywhere" , "Found everywhere" .)