Quietly put on attire for exploration (5)
I believe the answer is:
probe
'exploration' is the definition.
(probe is a kind of exploration)
'quietly put on attire' is the wordplay.
'quietly' becomes 'p' (p for piano and quiet).
'put on' means one lot of letters go next to another.
'attire' becomes 'robe' (I have seen 'Formal attire' mean 'robe' so perhaps 'attire' could also mean 'robe').
'p'+'robe'='PROBE'
'for' acts as a link.
(Other definitions for probe that I've seen before include "Closely enquire into" , "(Crime) investigation" , "sound" , "Question or examine thoroughly" , "Poke into" .)