Commercial almost exceedingly bold: scandalously, perhaps? (6)
I believe the answer is:
adverb
'scandalously perhaps?' is the definition.
(part of speech of "scandalously")
'commercial almost exceedingly bold' is the wordplay.
'commercial' becomes 'ad' (abbreviation for advertisement).
'almost' means to remove the last letter (most of the word but not all of it).
'exceedingly' becomes 'very' (I've seen this before).
'bold' becomes 'b' (abbreviation).
'very' with its last letter taken off is 'ver'.
'ad'+'ver'+'b'='ADVERB'
(Other definitions for adverb that I've seen before include "Modifying word (gram.)" , "Term of modification" , "Part of speech often ending in -ly" , "Braved (anag)" , "Word to qualify an action" .)