Your options include:
- Resize the partitions to make the /system partition larger (take out the SD card, plug in to PC, use any partitioning tool such as GParted).
- Find an older version of Google Play Services, they used to be much smaller. There must be one somewhere attached to a post on XDA Developers. Search via Google with site:forum.xda-developers.com or site:androidfilehost.com.
- Contact the author to get an APK version that works without the Play Store. If the app you want to use is GoldenDict it's certainly possible.
There are other ways too but if the app is not abandoned and the author can be contacted I'd try the above ones first.