Adult introducing bridge partners gets a little formidable (7)
I believe the answer is:
awesome
'formidable' is the definition.
(synonyms)
'adult introducing bridge partners gets a little' is the wordplay.
'introducing' says to take the initial letters (I've seen 'introduced' mean this).
'bridge partners' becomes 'we' (West and East are players in the card game bridge).
'gets' says to put letters next to each other.
'a little' becomes 'some' (both can mean a small amount).
The first letter of 'adult' is 'a'.
'a'+'we'+'some'='AWESOME'
(Other definitions for awesome that I've seen before include "Mighty" , "Inspiring admiration - wonderful!" , "Very imposing, inspiring wonder" , "Inspiring admiration or wonder" , "Overwhelming or dreadful to behold" .)