Elderly relative without a seat bored by daughter's showy play (13)
I believe the answer is:
grandstanding
'elderly relative without a seat bored by daughter's showy play' is the definition.
I can't tell whether this definition defines the answer.
'elderly relative without a seat bored by daughter's' is the wordplay.
'elderly relative' becomes 'gran' (short for grandmother).
'without a seat' becomes 'standing' (I can't explain this - if you can you should give a lot more credence to this answer).
'bored by' is an insertion indicator (inserted letters bore into the word).
'daughter' becomes 'd' (genealogical abbreviation).
'gran'+'standing'='granstanding'
'granstanding' placed around 'd' is 'GRANDSTANDING'.
Can you help me to learn more?
(Other definitions for grandstanding that I've seen before include "Trying to impress" , "Seeking to attract favourable publicity" , "Showing off" .)