Apostle includes building a counter (9)
I believe the answer is:
pedometer
'a counter' is the definition.
(I have seen 'Counter of paces ' mean 'pedometer' so perhaps 'counter' could also mean 'pedometer')
'apostle includes building' is the wordplay.
'apostle' becomes 'Peter' (Peter is an example).
'includes' is an insertion indicator.
'building' becomes 'dome' (I've seen this before).
'peter' enclosing 'dome' is 'PEDOMETER'.
(Other definitions for pedometer that I've seen before include "Measure of progress" , "Instrument for counting paces" , "Instrument for recording the number of steps" , "Walker's distance measurer" , "Walkers' measuring device" .)